Methods and compositions for treating hepatitis C virus using 4&#39;-modified nucleosides

ABSTRACT

A compound, method and composition for treating a host infected with a hepatitis C viral comprising administering an effective hepatitis C treatment amount of a described 4′-disubstituted nucleoside or a pharmaceutically acceptable salt or prodrug thereof, is provided.

FIELD OF THE INVENTION

[0001] This invention is in the area of pharmaceutical chemistry, and isin particular, is a compound, method and composition for the treatmentof hepatitis C virus and other viruses that replicate through anRNA-dependent RNA viral polymerase. This application claims priority toU.S. patent application Ser. No. 60/326,184.

BACKGROUND OF THE INVENTION

[0002] The hepatitis C virus (HCV) is the leading cause of chronic liverdisease worldwide. (Boyer, N. et al. J. Hepatol. 32:98-112, 2000). HCVcauses a slow growing viral infection and is the major cause ofcirrhosis and hepatocellular carcinoma (Di Besceglie, A. M. and Bacon,B. R., Scientific American, October: 80-85, (1999); Boyer, N. et al. J.Hepatol. 32:98-112, 2000). An estimated 170 million persons are infectedwith HCV worldwide. (Boyer, N. et al. J. Hepatol. 32:98-112, 2000).Cirrhosis caused by chronic hepatitis C infection accounts for8,000-12,000 deaths per year in the United States, and HCV infection isthe leading indication of liver transplantation.

[0003] HCV is known to cause at least 80% of posttransfusion hepatitisand a substantial proportion of sporadic acute hepatitis. Preliminaryevidence also implicates HCV in many cases of “idiopathic” chronichepatitis, “cryptogenic” cirrhosis, and probably hepatocellularcarcinoma unrelated to other hepatitis viruses, such as hepatitis Bvirus (HBV). A small proportion of healthy persons appear to be chronicHCV carriers, varying with geography and other epidemiological factors.The numbers may substantially exceed those for HBV, though informationis still preliminary; how many of these persons have subclinical chronicliver disease is unclear. (The Merck Manual, ch. 69, p. 901, 16th ed.,(1992)).

[0004] HCV has been classified as a member of the virus familyFlaviviridae that includes the genera flaviviruses, pestiviruses, andhepaciviruses which includes hepatitis C virus (Rice, C. M.,Flaviviridae: The viruses and their replication. In: Fields Virology,Editors: Fields, B. N., Knipe, D. M., and Howley, P. M.,Lippincott-Raven Publishers, Philadelphia, Pa., Chapter 30, 931-959,1996). HCV is an enveloped virus containing a positive-sensesingle-stranded RNA genome of approximately 9.4 kb. The viral genomeconsists of a 5′ untranslated region (UTR), a long open reading frameencoding a polyprotein precursor of approximately 3011 amino acids, anda short 3′ UTR. The 5′ UTR is the most highly conserved part of the HCVgenome and is important for the initiation and control of polyproteintranslation. Translation of the HCV genome is initiated by acap-independent mechanism known as internal ribosome entry. Thismechanism involves the binding of ribosomes to an RNA sequence known asthe internal ribosome entry site (IRES). An RNA pseudoknot structure hasrecently been determined to be an essential structural element of theUCV IRES. Viral structural proteins include a nucleocapsid core protein(C) and two envelope glycoproteins, E1 and E2. HCV also encodes twoproteinases, a zinc-dependent metalloproteinase encoded by the NS2-NS3region and a serine proteinase encoded in the NS3 region. Theseproteinases are required for cleavage of specific regions of theprecursor polyprotein into mature peptides. The carboxyl half ofnonstructural protein 5, NS5B, contains the RNA-dependent RNApolymerase. The function of the remaining nonstructural proteins, NS4Aand NS4B, and that of NS5A (the amino-terminal half of nonstructuralprotein 5) remain unknown.

[0005] A significant focus of current antiviral research is directedtoward the development of improved methods of treatment of chronic HCVinfections in humans (Di Besceglie, A. M. and Bacon, B. R., ScientificAmerican, October: 80-85, (1999)). Currently, there are two primaryantiviral compounds, ribavirin and interferon-alpha, which are used forthe treatment of chronic HCV infections in humans.

[0006] Treatment of HCV Infection with Ribavarin and Interferon

[0007] Ribavirin (1-β-D-ribofuranosyl-1-1,2,4-triazole-3-carboxamide) isa synthetic, non-interferon-inducing, broad spectrum antiviralnucleoside analog sold under the trade name, Virazole™ (The Merck Index,11th edition, Editor: Budavari, S., Merck & Co., Inc., Rahway, N.J.,p1304, 1989). U.S. Pat. No. 3,798,209 and RE29,835 disclose and claimribavirin. Ribavirin is structurally similar to guanosine, and has invitro activity against several DNA and RNA viruses includingFlaviviridae (Gary L. Davis. Gastroenterology 118:S104-S114, 2000).

[0008] Ribavirin reduces serum amino transferase levels to normal in 40%or patients, but it does not lower serum levels of HCV-RNA (Gary L.Davis. Gastroenterology 118:S104-S114, 2000). Thus, ribavirin alone isnot effective in reducing viral RNA levels. Additionally, ribavirin hassignificant toxicity and is known to induce anemia.

[0009] Interferons (IFNs) are compounds that have been commerciallyavailable for the treatment of chronic hepatitis for nearly a decade.IFNs are glycoproteins produced by immune cells in response to viralinfection. IFNs inhibit viral replication of many viruses, includingHCV, and when used as the sole treatment for hepatitis C infection, IFNsuppresses serum HCV-RNA to undetectable levels. Additionally, IFNnormalizes serum amino transferase levels. Unfortunately, the effects ofIFN are temporary and a sustained response occurs in only 8%-9% ofpatients chronically infected with HCV (Gary L. Davis. Gastroenterology118:S104-S114, 2000).

[0010] A number of patents disclose HCV treatments usinginterferon-based therapies. For example, U.S. Pat. No. 5,980,884 toBlatt et al. discloses methods for retreatment of patients afflictedwith HCV using consensus interferon. U.S. Pat. No. 5,942,223 to Bazer etal. discloses an anti-HCV therapy using ovine or bovine interferon-tau.U.S. Pat. No. 5,928,636 to Alber et al. discloses the combinationtherapy of interleukin-12 and interferon alpha for the treatment ofinfectious diseases including HCV. U.S. Pat. No. 5,908,621 to Glue etal. discloses the use of polyethylene glycol modified interferon for thetreatment of HCV. U.S. Pat. No. 5,849,696 to Chretien et al. disclosesthe use of thymosins, alone or in combination with interferon, fortreating HCV. U.S. Pat. No. 5,830,455 to Valtuena et al. discloses acombination HCV therapy employing interferon and a free radicalscavenger. U.S. Pat. No. 5,738,845 to Imakawa discloses the use of humaninterferon tau proteins for treating HCV. Other interferon-basedtreatments for HCV are disclosed in U.S. Pat. No. 5,676,942 to Testa etal., U.S. Pat. No. 5,372,808 to Blatt et al., and U.S. Pat. No.5,849,696.

[0011] Combination of Interferon and Ribavirin

[0012] Schering-Plough sells ribavirin as Rebetol® capsules (200 mg) foradministration to patients with HCV. The U.S. FDA has approved Rebetolcapsules to treat chronic HCV infection in combination with Schering'salpha interferon products Intron® A and PEG-Intron™. Rebetol capsulesare not approved for monotherapy (i.e., administration independent ofIntron A or PEG-Intron), although Intron A and PEG-Intron are approvedfor monotherapy (i.e., administration without ribavirin). Hoffman LaRoche is selling ribavirin under the name CoPegus, also for use incombination with interferon for the treatment of HCV. Other alphainterferon products are Roferon-A (Hoffmann-La Roche), Infergen®(Intermune, formerly Amgen's product), and Wellferon® (WellcomeFoundation) are currently FDA-approved for HCV monotherapy.

[0013] Additional References Disclosing Methods to Treat HCV Infections

[0014] A number of HCV treatments are reviewed by Bymock et al. inAntiviral Chemistry & Chemotherapy, 11:2; 79-95 (2000).

[0015] Several substrate-based NS3 protease inhibitors have beenidentified in the literature, in which the scissile amide bond of acleaved substrate is replaced by an electrophile, which interacts withthe catalytic serine. Attwood et al. (1998) Antiviral peptidederivatives, 98/22496; Attwood et al. (1999), Antiviral Chemistry andChemotherapy 10.259-273; Attwood et al. (1999) Preparation and use ofamino acid derivatives as anti-viral agents, German Patent PublicationDE 19914474; Tung et al. (1998) Inhibitors of serine proteases,particularly hepatitis C virus NS3 protease, WO 98/17679. The reportedinhibitors terminate in an electrophile such as a boronic acid orphosphonate. Llinas-Brunet et al. (1999) Hepatitis C inhibitor peptideanalogues, WO 99/07734. Two classes of electrophile-based inhibitorshave been described, alphaketoamides and hydrazinoureas.

[0016] The literature has also described a number of non-substrate-basedinhibitors. For example, evaluation of the inhibitory effects of2,4,6-trihydroxy-3-nitro-benzamide derivatives against HCV protease andother serine proteases has been reported. Sudo, K. et al., (1997)Biochemical and Biophysical Research Communications, 238:643-647; Sudo,K. et al. (1998) Antiviral Chemistry and Chemotherapy 9:186. Using areverse-phase HPLC assay, the two most potent compounds identified wereRD3-4082 and RD3-4078, the former substituted on the amide with a 14carbon chain and the latter processing a para-phenoxyphenyl group.

[0017] Thiazolidine derivatives have been identified as micromolarinhibitors, using a reverse-phase HPLC assay with an NS3/4A fusionprotein and NS5A/5B substrate. Sudo, K. et al. (1996) Antiviral Research32:9-18. Compound RD-1-6250, possessing a fused cinnamoyl moietysubstituted with a long alkyl chain, was the most potent against theisolated enzyme. Two other active examples were RD4 6205 and RD4 6193.

[0018] Other literature reports screening of a relatively small libraryusing an ELISA assay and the identification of three compounds as potentinhibitors, a thiazolidine and two benzanilides. Kakiuchi N. et al. J.EBS Letters 421:217-220; Takeshita N. et al., Analytical Biochemistry247:242-246, 1997. Several U.S. patents disclose protease inhibitors forthe treatment of HCV. For example, U.S. Pat. No. 6,004,933 to Spruce etal. discloses a class of cysteine protease inhibitors for inhibiting HCVendopeptidase 2. U.S. Pat. No. 5,990,276 to Zhang et al. disclosessynthetic inhibitors of hepatitis C virus NS3 protease. The inhibitor isa subsequence of a substrate of the NS3 protease or a substrate of theNS4A cofactor. The use of restriction enzymes to treat HCV is disclosedin U.S. Pat. No. 5,538,865 to Reyes et al.

[0019] Isolated from the fermentation culture broth of Streptomyces sp.,Sch 68631, a phenan-threnequinone, possessed micromolar activity againstHCV protease in a SDS-PAGE and autoradiography assay. Chu M. et al.,Tetrahedron Letters 37:7229-7232, 1996. In another example by the sameauthors, Sch 351633, isolated from the fungus Penicillium griscofuluum,demonstrated micromolar activity in a scintillation proximity assay. ChuM. et al., Bioorganic and Medicinal Chemistry Letters 9:1949-1952.Nanomolar potency against the HCV NS3 protease enzyme has been achievedby the design of selective inhibitors based on the macromolecule eglinc. Eglin c, isolated from leech, is a potent inhibitor of several serineproteases such as S. griseus proteases A and B, α-chymotrypsin, chymaseand subtilisin. Qasim M. A. et al., Biochemistry 36:1598-1607, 1997.

[0020] HCV helicase inhibitors have also been reported. U.S. Pat. No.5,633,358 to Diana G. D. et al.; PCT Publication No. WO 97/36554 ofDiana G. D. et al.. There are a few reports of HCV polymeraseinhibitors: some nucleotide analogues, gliotoxin and the natural productcerulenin. Ferrari R. et al., Journal of Virology 73:1649-1654, 1999;Lohmann V. et al., Virology 249:108-118, 1998.

[0021] Antisense phosphorothioate oligodeoxynucleotides complementary tosequence stretches in the 5′ non-coding region of the HCV, are reportedas efficient inhibitors of HCV gene expression in in vitro translationand IIcpG2 IICV-luciferase cell culture systems. Alt M. et al.,Hepatology 22:707-717, 1995. Recent work has demonstrated thatnucleotides 326-348 comprising the 3′ end of the NCR and nucleotides371-388 located in the core coding region of the HCV RNA are effectivetargets for antisense-mediated inhibition of viral translation. Alt M.et al., Archives of Virology 142:589-599, 1997. U.S. Pat. No. 6,001,990to Wands et al. discloses oligonucleotides for inhibiting thereplication of HCV. PCT Publication No. WO 99/29350 disclosescompositions and methods of treatment for hepatitis C infectioncomprising the administration of antisense oligonucleotides that arecomplementary and hybridizable to HCV-RNA. U.S. Pat. No. 5,922,857 toHan et al. disclose nucleic acids corresponding to the sequence of thepestivirus homology box IV area for controlling the translation of HCV.Antisense oligonucleotides as therapeutic agents have been recentlyreviewed (Galderisi U. et al., Journal of Cellular Physiology181:251-257, 1999).

[0022] Other compounds have been reported as inhibitors ofIRES-dependent translation in HCV. Japanese Patent PublicationJP-08268890 of Ikeda N et al.; Japanese Patent Publication JP-10101591of Kai, Y. et al. Nuclease-resistant ribozymes have been targeted at theIRES and recently reported as inhibitors in an HCV-poliovirus chimeraplaque assay. Maccjak D. J. et al., Hepatology 30 abstract 995, 1999.The use of ribozymes to treat HCV is also disclosed in U.S. Pat. No.6,043,077 to Barber et al., and U.S. Pat. Nos. 5,869,253 and 5,610,054to Draper et al.

[0023] Other patents disclose the use of immune system potentiatingcompounds for the treatment of HCV. For example, U.S. Pat. No. 6,001,799to Chretien et al. discloses a method of treating hepatitis C innon-responders to interferon treatment by administering an immune systempotentiating dose of thymosin or a thymosin fragment. U.S. Pat. Nos.5,972,347 to Eder et al. and 5,969,109 to Bona et al. discloseantibody-based treatments for treating HCV.

[0024] U.S. Pat. No. 6,034,134 to Gold et al. discloses certain NMDAreceptor agonists having immunodulatory, antimalarial, anti-Borna virusand anti-Hepatitis C activities. The disclosed NMDA receptor agonistsbelong to a family of 1-amino-alkylcyclohexanes. U.S. Pat. No. 6,030,960to Morris-Natschke et al. discloses the use of certain alkyl lipids toinhibit the production of hepatitis-induced antigens, including thoseproduced by the HCV virus. U.S. Pat. No. 5,922,757 to Chojkier et al.discloses the use of vitamin E and other antioxidants to treat hepaticdisorders including HCV. U.S. Pat. No. 5,858,389 to Elsherbi et al.discloses the use of squalene for treating hepatitis C. U.S. Pat. No.5,849,800 to Smith et al discloses the use of amantadine for treatmentof Hepatitis C. U.S. Pat. No. 5,846,964 to Ozeki et al. discloses theuse of bile acids for treating HCV. U.S. Pat. No. 5,491 ,135 to Bloughet al. discloses the use of N-(phosphonoacetyl)-L-aspartic acid to treatflaviviruses such as HCV.

[0025] Other compounds proposed for treating HCV include plant extracts(U.S. Pat. No. 5,837,257 to Tsai et al., U.S. Pat. No. 5,725,859 to Omeret al., and U.S. Pat. No. 6,056,961), piperidenes (U.S. Pat. No.5,830,905 to Diana et al.), benzenedicarboxamides (U.S. Pat. No.5,633,388 to Diana et al.), polyadenylic acid derivatives (U.S. Pat. No.5,496,546 to Wang et al.), 2′,3′-dideoxyinosine (U.S. Pat. No. 5,026,687to Yarchoan et al.), benzimidazoles (U.S. Pat. No. 5,891,874 to Colacinoet al.).

[0026] Other agents developed for the treatment of HCV includes PEGASYS(pegylated interferon alfa-2a) by Roche, INFERGEN (interferon alfacon-1)by InterMune, OMNIFERON (natural interferon) by Viragen, ALBUFERON byHuman Genome Sciences, REBIF (interferon beta-1a) by Ares-Serono, OmegaInterferon by BioMedicine, Oral Interferon Alpha by AmarilloBiosciences, Interferon gamma-1b by InterMune, Interleukin-10 bySchering-Plough, IP-501 by Interneuron, Merimebodib VX-497 by Vertex,AMANTADINE (Symmetrel) by Endo Labs Solvay, HEPTAZYME by RPI, IDN-6556by Idun Pharma., XTL-002 by XTL., HCV/MF59 by Chiron, CIVACIR by NABI,LEVOVIRIN by ICN, VIRAMIDINE by ICN, ZADAXIN (thymosin alfa-1) by SciClone, CEPLENE (histamine dihydrochloride) by Maxim, VX 950/LY 570310 byVertex/Eli Lilly, ISIS 14803 by Isis Pharmaceutical/Elan, IDN-6556 byIdun Pharmaceuticals, Inc. and JTK 003 by AKROS Pharma.

[0027] Idenix Pharmaceuticals, Ltd. was first to disclose branchednucleosides, and their use in the treatment of HCV and flaviviruses andpestiviruses in International Publication Nos. WO 01/90121 and WO01/92282.

[0028] A method for the treatment of hepatitis C infection (andflaviviruses and pestiviruses) in humans and other host animals isdisclosed in the Idenix publications that includes administering aneffective amount of a biologically active 1′, 2′, or 3′-branched β-D orβ-L nucleosides or a pharmaceutically acceptable salt or prodrugthereof, administered either alone or in combination, optionally in apharmaceutically acceptable carrier.

[0029] WO 01/96353 to Indenix Pharmaceuticals, Ltd. discloses3′-prodrugs of 2′-deoxy-β-L-nucleosides for the treatment of HBV. U.S.Pat. No. 4,957,924 to Beauchamp discloses various therapeutic esters ofacyclovir.

[0030] Other patent applications disclosing the use of certainnucleoside analogs to treat hepatitis C virus include: PCT/CA00/01316(WO 01/32153) and PCTCA01/00197 (WO 01/60315) filed by BioChem Pharma,Inc. (now Shire Biochem, Inc.); PCT/US02/01531 (WO 02/057425 A2) andPCT/US02/03086 (WO 02/057287) filed by Merck & Co., Inc., andPCTEP01/09633 (WO 02/18404) filed by Hoffman La Roche.

[0031] In light of the fact that the hepatitis C virus has reachedepidemic levels worldwide, and has tragic effects on the infectedpatient, there remains a strong need to provide new effectivepharmaceutical agents to treat hepatitis C that has low toxicity to thehost.

[0032] Therefore, it is an object of the present invention to provide acompound, method and composition for the treatment of a host infectedwith hepatitis C virus.

SUMMARY OF THE INVENTION

[0033] Compounds, methods and compositions for the treatment ofhepatitis C infection are described that include an effective hepatitisC treatment amount of a β-D- or β-L-nucleoside of the Formulas (I)-(VI),or a pharmaceutically acceptable salt or prodrug thereof. Thesecompounds can also be used generally as inhibitors of RNA-dependent RNAviral polymerase.

[0034] In a first principal embodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is provided:

[0035] wherein:

[0036] R¹, R² and R³ are independently H, phosphate (including mono-,di- or triphosphate and a stabilized phosphate prodrug); acyl (includinglower acyl); alkyl (including lower alkyl); sulfonate ester includingalkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl,wherein the phenyl group is optionally substituted with one or moresubstituents as described in the definition of aryl given herein; alipid, including a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² or R³ is independently H or phosphate;

[0037] Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;

[0038] X¹ and X² are independently selected from the group consisting ofH, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and

[0039] R⁴ and R⁵ are independently hydrogen, acyl (including loweracyl), or alkyl (including but not limited to methyl, ethyl, propyl andcyclopropyl).

[0040] In a second principal embodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is provided:

[0041] wherein:

[0042] R¹, R² and R³ are independently H, phosphate (including mono-,di- or triphosphate and a stabilized phosphate prodrug); acyl (includinglower acyl); alkyl (including lower alkyl); sulfonate ester includingalkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl,wherein the phenyl group is optionally substituted with one or moresubstituents as described in the definition of aryl given herein; alipid, including a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² or R³ is independently H or phosphate;

[0043] Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;

[0044] X¹ is selected from the group consisting of H, straight chained,branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and

[0045] R⁴ and R⁵ are independently hydrogen, acyl (including loweracyl), or alkyl (including but not limited to methyl, ethyl, propyl andcyclopropyl).

[0046] In a third principal embodiment, a compound selected fromFormulas III, IV and V, or a pharmaceutically acceptable salt or prodrugthereof, is provided:

[0047] wherein:

[0048] Base is a purine or pyrimidine base as defined herein;

[0049] R¹, R² and R³ are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² or R³ is independently H orphosphate;

[0050] R⁶ is hydroxy, alkyl (including lower alkyl), azido, cyano,alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl), —C(O)O(loweralkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),—O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(loweralkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and

[0051] X is O, S, SO₂ or CH₂.

[0052] In a fourth principal embodiment the invention provides acompound of Formula VI, or a pharmaceutically acceptable salt or prodrugthereof:

[0053] wherein:

[0054] Base is a purine or pyrimidine base as defined herein;

[0055] R¹ and R² are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹ or R² is independently H or phosphate;

[0056] R⁶ is hydroxy, alkyl (including lower alkyl), azido, cyano,alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, —N(acyl)₂;

[0057] R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl(including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,—C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl),—O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;

[0058] R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),chlorine, bromine or iodine;

[0059] alternatively, R⁷ and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰can come together to form a pi bond; and

[0060] X is O, S, SO₂ or CH₂.

[0061] The β-D- and β-L-nucleosides of this invention may inhibit HCVpolymerase activity, and can be generally used as inhibitors ofRNA-dependent RNA viral polymerase. Nucleosides can be screened fortheir ability to inhibit HCV polymerase activity in vitro according toscreening methods set forth more particularly herein. One can readilydetermine the spectrum of activity by evaluating the compound in theassays described herein or with another confirmatory assay.

[0062] In one embodiment the efficacy of the anti-HCV compound ismeasured according to the concentration of compound necessary to reducethe plaque number of the virus in vitro, according to methods set forthmore particularly herein, by 50% (i.e. the compound's EC₅₀). Inpreferred embodiments the compound exhibits an EC₅₀ of less than 25, 15,10, 5, or 1 micromolar.

[0063] In another embodiment, the active compound can be administered incombination or alternation with another anti-HCV agent oranti-RNA-dependent RNA polymerase agent. In combination therapy, aneffective dosage of two or more agents are administered together,whereas during alternation therapy an effective dosage of each agent isadministered serially. The dosages will depend on absorption,inactivation, and excretion rates of the drug as well as other factorsknown to those of skill in the art. It is to be noted that dosage valueswill also vary with the severity of the condition to be alleviated. Itis to be further understood that for any particular subject, specificdosage regimens and schedules should be adjusted over time according tothe individual need and the professional judgment of the personadministering or supervising the administration of the compositions.

BRIEF DESCRIPTION OF THE FIGURES

[0064]FIG. 1 provides the structure of various non-limiting examples ofnucleosides of the present invention, as well as other knownnucleosides, FIAU and Ribavirin, which are used as comparative examplesin the text.

[0065]FIG. 2 is a non-limiting illustration of the synthesis of apentodialdo-furanose of the present invention,1-O-methyl-2,3-O-isopropylidene β-D-ribo-pentodialdo-furanose (2) and a4′-modified sugar of the present invention,5-O-benzoyl-4-C-methyl-1,2,3-O-acetyl-α,β-D-ribofuranose (7).

[0066]FIG. 3 is a non-limiting illustration of the synthesis of various4′-modified pyrimidine nucleoside of the present invention, including1-(4-C-methyl-α,β-D-ribofuranosyl)-uracil (9),1-(4-C-methyl-β-D-ribofuranosyl)4-thio-uracil (11) and1-(4-C-methyl-β-D-ribo-furanosyl)thymine (14); and pharmaceuticallyacceptable salts, including 1-(4-C-methyl-β-D-ribofuranosyl)cytosine,hydrochloric form (12) and1-(4-C-methyl-β-D-ribofuranosyl)-5-methyl-cytosine, hydrochloride form(17).

[0067]FIG. 4 is a non-limiting illustration of the synthesis of a4′-modified purine nucleoside of the present invention,9-(4-C-methyl-β-D-ribofuranosyl) guanine (19).

[0068]FIG. 5 is a non-limiting illustration of the synthesis of a4′-modified purine nucleoside of the present invention,9-(4-C-methyl-β-D-ribofuranosyl) adenine (21).

DETAILED DESCRIPTION OF THE INVENTION

[0069] The invention as disclosed herein is a compound, method andcomposition for the treatment of hepatitis C in humans or other hostanimals, that includes administering an effective HCV treatment amountof a β-D- or β-L-nucleoside as described herein or a pharmaceuticallyacceptable salt or prodrug thereof, optionally in a pharmaceuticallyacceptable carrier. The compounds of this invention either possessantiviral (i.e., anti-HCV) activity, or are metabolized to a compoundthat exhibits such activity. In an alternative embodiment, the compoundscan be used generally to inhibit RNA-dependent RNA viral polymerase.

[0070] In summary, the present invention includes the followingfeatures:

[0071] (a) β-D- and β-L-nucleosides, as described herein, andpharmaceutically acceptable salts and prodrugs thereof;

[0072] (b) β-D- and β-L-nucleosides as described herein, andpharmaceutically acceptable salts and prodrugs thereof for use in thetreatment or prophylaxis of an HCV infection, especially in individualsdiagnosed as having an HCV infection or being at risk for becominginfected by HCV;

[0073] (c) use of these β-D- and β-L-nucleosides, and pharmaceuticallyacceptable salts and prodrugs thereof in the manufacture of a medicamentfor treatment of an HCV infection;

[0074] (d) pharmaceutical formulations comprising the β-D- orβ-L-nucleosides or pharmaceutically acceptable salts or prodrugs thereoftogether with a pharmaceutically acceptable carrier or diluent;

[0075] (e) β-D- and β-L-nucleosides as described herein substantially inthe absence of enantiomers of the described nucleoside, or substantiallyisolated from other chemical entities;

[0076] (f) processes for the preparation of β-D- and β-L-nucleosides, asdescribed in more detail below; and

[0077] (g) processes for the preparation of β-D- and β-L-nucleosidessubstantially in the absence of enantiomers of the described nucleoside,or substantially isolated from other chemical entities.

[0078] I. Active Compound, and Physiologically Acceptable Salts andProdrugs Thereof

[0079] In a first principal embodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is provided:

[0080] wherein:

[0081] R¹, R² and R³ are independently H, phosphate (including mono-,di- or triphosphate and a stabilized phosphate prodrug); acyl (includinglower acyl); alkyl (including lower alkyl); sulfonate ester includingalkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl,wherein the phenyl group is optionally substituted with one or moresubstituents as described in the definition of aryl given herein; alipid, including a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² or R³ is independently H or phosphate;

[0082] Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;

[0083] X¹ and X² are independently selected from the group consisting ofH, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and

[0084] R⁴ and R⁵ are independently hydrogen, acyl (including loweracyl), or alkyl (including but not limited to methyl, ethyl, propyl andcyclopropyl).

[0085] In a preferred subembodiment, a compound of Formula I, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

[0086] R¹, R² and R³ are independently H or phosphate (preferably H);

[0087] X¹ is H;

[0088] X² is H or NH₂; and

[0089] Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

[0090] In a second principal embodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is provided:

[0091] wherein:

[0092] R¹, R² and R³ are independently H, phosphate (including mono-,di- or triphosphate and a stabilized phosphate prodrug); acyl (includinglower acyl); alkyl (including lower alkyl); sulfonate ester includingalkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl,wherein the phenyl group is optionally substituted with one or moresubstituents as described in the definition of aryl given herein; alipid, including a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² or R³ is independently H or phosphate;

[0093] Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴;

[0094] X¹ is selected from the group consisting of H, straight chained,branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁵; and

[0095] R⁴ and R⁵ are independently hydrogen, acyl (including loweracyl), or alkyl (including but not limited to methyl, ethyl, propyl andcyclopropyl).

[0096] In a preferred subembodiment, a compound of Formula II, or apharmaceutically acceptable salt or prodrug thereof, is providedwherein:

[0097] R¹, R² and R³ are independently H or phosphate (preferably H);

[0098] X¹ is H or CH₃; and

[0099] Y is hydrogen, bromo, chloro, fluoro, iodo, NH₂ or OH.

[0100] In a third principal embodiment, a compound selected fromFormulas III, IV and V, or a pharmaceutically acceptable salt or prodrugthereof, is provided:

[0101] wherein:

[0102] Base is a purine or pyrimidine base as defined herein;

[0103] R¹, R² and R³ are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² or R³ is independently H orphosphate;

[0104] R⁶ is hydroxy, alkyl (including lower alkyl), azido, cyano,alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl), —C(O)O(loweralkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl),—O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(loweralkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and

[0105] X is O, S, SO₂ or CH₂.

[0106] In a first preferred subembodiment, a compound of Formula III, IVor V, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

[0107] Base is a purine or pyrimidine base as defined herein;

[0108] R¹, R² and R³ are independently hydrogen or phosphate;

[0109] R⁶ is alkyl; and

[0110] X is O, S, SO₂ or CH₂.

[0111] In a second preferred subembodiment, a compound of Formula III,IV or V, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

[0112] Base is a purine or pyrimidine base as defined herein;

[0113] R¹, R² and R³ are hydrogens;

[0114] R⁶ is alkyl; and

[0115] X is O, S, SO₂ or CH₂.

[0116] In a third preferred subembodiment, a compound of Formula III, IVor V, or a pharmaceutically acceptable salt or prodrug thereof, isprovided wherein:

[0117] Base is a purine or pyrimidine base as defined herein;

[0118] R¹, R² and R³ are independently hydrogen or phosphate;

[0119] R⁶ is alkyl; and

[0120] X is O.

[0121] In even more preferred subembodiments, a compound of Formula IV,or its pharmaceutically acceptable salt or prodrug, is provided:

[0122] wherein:

[0123] Base is a purine or pyrimidine base as defined herein; optionallysubstituted with an amine or cyclopropyl (e.g., 2-amino, 2,6-diamino orcyclopropyl guanosine); and

[0124] R¹ and R² are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹ or R² is independently H or phosphate.

[0125] In a fourth principal embodiment the invention provides acompound of Formula VI, or a pharmaceutically acceptable salt or prodrugthereof:

[0126] wherein:

[0127] Base is a purine or pyrimidine base as defined herein;

[0128] R¹ and R² are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹ or R² is independently H or phosphate;

[0129] R⁶ is hydroxy, alkyl (including lower alkyl), azido, cyano,alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, —N(acyl)₂;

[0130] R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl(including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,—C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl),—O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;

[0131] R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),chlorine, bromine or iodine;

[0132] alternatively, R⁷ and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰can come together to form a pi bond; and

[0133] X is O, S, SO₂ or CH₂.

[0134] In a first preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine, or iodine; and (6) X is O,S, SO₂ or CH₂.

[0135] In a second preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino, or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine, or iodine; and (6) X is O, S, SO₂ orCH₂.

[0136] In a third preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are H; and (6) X is O, S, SO₂ orCH₂.

[0137] In a fourth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl, alkenyl, alkynyl,Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo, fluoro, iodo, NO₂,amino, loweralkylamino, or di(loweralkyl)amino; (4) R⁷ and R⁹ areindependently OR², alkyl, alkenyl, alkynyl, Br-vinyl, O-alkenyl,chlorine, bromine, iodine, NO₂, amino, loweralkylamino, ordi(loweralkyl)amino; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine, or iodine; and (6) X is O.

[0138] In a fifth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR¹; (5) R⁸ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine or iodine; and (6) X is O, S, SO₂ orCH₂.

[0139] In a sixth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino, or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are H; and (6) Xis O, S, SO₂, or CH₂.

[0140] In a seventh preferred subembodiment, a compound of Formula VI,or its pharmaceutically acceptable salt or prodrug, is provided inwhich: (1) Base is a purine or pyrimidine base as defined herein; (2) R¹is independently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are independentlyH, alkyl (including lower alkyl), chlorine, bromine or iodine; and (6) Xis O.

[0141] In a eighth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are hydrogen; and (6) X isO, S, SO₂ or CH₂.

[0142] In a ninth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are independently H, alkyl(including lower alkyl), chlorine, bromine or iodine; and (6) X is O.

[0143] In a tenth preferred subembodiment, a compound of Formula VI, orits pharmaceutically acceptable salt or prodrug, is provided in which:(1) Base is a purine or pyrimidine base as defined herein; (2) R¹ isindependently H or phosphate (including monophosphate, diphosphate,triphosphate, or a stabilized phosphate prodrug); acyl (including loweracyl); alkyl (including lower alkyl); sulfonate ester including alkyl orarylalkyl sulfonyl including methanesulfonyl and benzyl, wherein thephenyl group is optionally substituted with one or more substituents asdescribed in the definition of aryl given herein; a lipid, including aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ isindependently H or phosphate; (3) R⁶ is alkyl (including lower alkyl),alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro, bromo,fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino; (4) R⁷and R⁹ are independently OR², alkyl (including lower alkyl), alkenyl,alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino, or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are hydrogen;and (6) X is O.

[0144] In an eleventh preferred subembodiment, a compound of Formula VI,or its pharmaceutically acceptable salt or prodrug, is provided inwhich: (1) Base is a purine or pyrimidine base as defined herein; (2) R¹is independently H or phosphate; (3) R⁶ is alkyl (including loweralkyl), alkenyl, alkynyl, Br-vinyl, hydroxy, O-alkyl, O-alkenyl, chloro,bromo, fluoro, iodo, NO₂, amino, loweralkylamino or di(loweralkyl)amino;(4) R⁷ and R⁹ are independently OR²; (5) R⁸ and R¹⁰ are hydrogen; and(6) X is O, S, SO₂ or CH₂.

[0145] In a twelfth preferred subembodiment, a compound of Formula VI,or its pharmaceutically acceptable salt or prodrug, is provided inwhich: (1) Base is a purine or pyrimidine base as defined herein; (2) R¹is independently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O, S, SO₂,or CH₂.

[0146] In a thirteenth preferred subembodiment, a compound of FormulaVI, or its pharmaceutically acceptable salt or prodrug, is provided inwhich: (1) Base is a purine or pyrimidine base as defined herein; (2) R¹is independently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR²; (5) R¹ and R¹⁰ are independently H, alkyl (includinglower alkyl), chlorine, bromine, or iodine; and (6) X is O.

[0147] In a fourteenth preferred subembodiment, a compound of FormulaVI, or its pharmaceutically acceptable salt or prodrug, is provided inwhich: (1) Base is a purine or pyrimidine base as defined herein; (2) R¹is independently H or phosphate; (3) R⁶ is alkyl; (4) R⁷ and R⁹ areindependently OR², alkyl (including lower alkyl), alkenyl, alkynyl,Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO₂, amino,loweralkylamino or di(loweralkyl)amino; (5) R⁸ and R¹⁰ are hydrogen; and(6) X is O.

[0148] In even more preferred subembodiments, a compound of Formula VI,or its pharmaceutically acceptable salt or prodrug, is provided inwhich:

[0149] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0150] (1) Base is guanine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0151] (1) Base is cytosine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4)R⁷ and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0152] (1) Base is thymine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0153] (1) Base is uracil; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0154] (1) Base is adenine; (2) R¹ is phosphate; (3) R⁶ is methyl; (4)R⁷ and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0155] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is ethyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0156] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is propyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0157] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is butyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is O;

[0158] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷is hydrogen and R⁹ is hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) Xis O;

[0159] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is S;

[0160] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is SO₂; or

[0161] (1) Base is adenine; (2) R¹ is hydrogen; (3) R⁶ is methyl; (4) R⁷and R⁹ are hydroxyl; (5) R⁸ and R¹⁰ are hydrogen; and (6) X is CH₂.

[0162] The β-D- and β-L-nucleosides of this invention may inhibit HCVpolymerase activity. Nucleosides can be screened for their ability toinhibit HCV polymerase activity in vitro according to screening methodsset forth more particularly herein. One can readily determine thespectrum of activity by evaluating the compound in the assays describedherein or with another confirmatory assay.

[0163] In one embodiment the efficacy of the anti-HCV compound ismeasured according to the concentration of compound necessary to reducethe plaque number of the virus in vitro, according to methods set forthmore particularly herein, by 50% (i.e. the compound's EC₅₀). Inpreferred embodiments the compound exhibits an EC₅₀ of less than 15 or10 micromolar, when measured according to the polymerase assay describedin Ferrari et al., Jnl. of Vir., 73:1649-1654, 1999; Ishii et al.,Hepatology, 29:1227-1235,1999; Lohmann et al., Jnl. of Bio. Chem.,274:10807-10815, 1999; or Yamashita et al, Jnl. of Bio. Chem.,273:15479-15486, 1998.

[0164] The active compound can be administered as any salt or prodrugthat upon administration to the recipient is capable of providingdirectly or indirectly the parent compound, or that exhibits activityitself. Nonlimiting examples are the pharmaceutically acceptable salts(alternatively referred to as “physiologically acceptable salts”), and acompound that has been alkylated or acylated at the 5′-position or onthe purine or pyrimidine base (a type of “pharmaceutically acceptableprodrug”). Further, the modifications can affect the biological activityof the compound, in some cases increasing the activity over the parentcompound. This can easily be assessed by preparing the salt or prodrugand testing its antiviral activity according to the methods describedherein, or other methods known to those skilled in the art.

[0165] II. Definitions

[0166] The term alkyl, as used herein, unless otherwise specified,refers to a saturated straight, branched, or cyclic, primary, secondary,or tertiary hydrocarbon of typically C₁ to C₁₀, and specificallyincludes methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl,t-butyl, pentyl, cyclopentyl, isopentyl, neopentyl, hexyl, isohexyl,cyclohexyl, cyclohexylmethyl, 3-methylpentyl, 2,2-dimethylbutyl, and2,3-dimethylbutyl. The term includes both substituted and unsubstitutedalkyl groups. Moieties with which the alkyl group can be substituted areselected from the group consisting of hydroxyl, halo (includingindependently F, Cl, Br, and I), amino, alkylamino, arylamino, alkoxy,aryloxy, nitro, cyano, carboxamido, carboxylate, thio, alkylthio, azido,sulfonic acid, sulfate, phosphonic acid, phosphate, or phosphonate,either unprotected, or protected as necessary, as known to those skilledin the art, for example, as taught in Greene, et al., Protective Groupsin Organic Synthesis, John Wiley and Sons, Second Edition, 1991, herebyincorporated by reference. In one embodiment, the alkyl can be, forexample, CF₃, CH₂CF₃, CCl₃, or cyclopropyl. In the text, whenever theterm C(alkyl range) is used, the term independently includes each memberof that class as if specifically and separately set out.

[0167] The term lower alkyl, as used herein, and unless otherwisespecified, refers to a C₁ to C₄ saturated straight, branched, or ifappropriate, a cyclic (for example, cyclopropyl) alkyl group, includingboth substituted and unsubstituted forms. Unless otherwise specificallystated in this application, when alkyl is a suitable moiety, lower alkylis preferred. Similarly, when alkyl or lower alkyl is a suitable moiety,unsubstituted alkyl or lower alkyl is preferred.

[0168] The term alkylamino or arylamino refers to an amino group thathas one or two alkyl or aryl substituents, respectively.

[0169] The term “protected” as used herein and unless otherwise definedrefers to a group that is added to an oxygen, nitrogen, or phosphorusatom to prevent its further reaction or for other purposes. A widevariety of oxygen and nitrogen protecting groups are known to thoseskilled in the art of organic synthesis.

[0170] The term aryl, as used herein, and unless otherwise specified,refers to phenyl, biphenyl, or naphthyl, and preferably phenyl. The termincludes both substituted and unsubstituted moieties. The aryl group canbe substituted with one or more moieties selected from the groupconsisting of alkyl, halo (independently F, Cl, Br, or I), hydroxyl,amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano,carboxamido, carboxylate, thio, alkylthio, sulfonic acid, sulfate,phosphonic acid, phosphate, or phosphonate, either unprotected, orprotected as necessary, as known to those skilled in the art, forexample, as taught in Greene, et al., Protective Groups in OrganicSynthesis, John Wiley and Sons, Second Edition, 1991.

[0171] The term alkaryl or alkylaryl refers to an alkyl group with anaryl substituent. The term aralkyl or arylalkyl refers to an aryl groupwith an alkyl substituent.

[0172] The term halo, as used herein, includes chloro, bromo, iodo, andfluoro.

[0173] The term purine or pyrimidine base includes, but is not limitedto, adenine, N⁶-alkylpurines, N⁶-acylpurines (wherein acyl isC(O)(alkyl, aryl, alkylaryl, or arylalkyl), N⁶-benzylpurine,N⁶-halopurine, N⁶-vinylpurine, N⁶-acetylenic purine, N⁶-acyl purine,N⁶-hydroxyalkyl purine, N⁶-thioalkyl purine, N²-alkylpurines,N²-alkyl-6-thiopurines, thymine, cytosine, 5-fluorocytosine,5-methylcytosine, 6-azapyrimidine, including 6-azacytosine, 2- and/or4-mercaptopyrmidine, uracil, 5-halouracil, including 5-fluorouracil,C⁵-alkylpyrimidines, C⁵-benzylpyrimidines, C⁵-halopyrimidines,C⁵-vinylpyrimidine, C⁵-acetylenic pyrimidine, C⁵-acyl pyrimidine,C⁵-hydroxyalkyl purine, C⁵-amidopyrimidine, C⁵-cyanopyrimidine,C⁵-nitropyrimidine, C⁵-aminopyrimidine, N²-alkylpurines,N²-alkyl-6-thiopurines, 5-azacytidinyl, 5-azauracilyl,triazolopyridinyl, imidazolopyridinyl, pyrrolopyrimidinyl,pyrazolopyrimidinyl,

[0174] wherein A, G, and L are each independently CH or N;

[0175] D is N, CH, C—CN, C—NO₂, C—C₁₋₃ alkyl, C—NHCONH₂, C—CONQ¹¹Q¹¹,C—CSNQ¹¹Q¹¹, CCOOQ¹¹, C—C(═NH)NH₂, C-hydroxy, C—C₁₋₃alkoxy, C-amino,C—C₁₋₄ alkylamino, C-di(C₁₋₄ alkyl)amino, C-halogen,C-(1,3-oxazol-2-yl), C-(1,3-thiazol-2-yl), or C-(imidazol-2-yl); whereinalkyl is unsubstituted or substituted with one to three groupsindependently selected from halogen, amino, hydroxy, carboxy, and C₁₋₃alkoxy;

[0176] E is N or CQ⁵;

[0177] W is O, S, or NR;

[0178] R is H, OH, alkyl;

[0179] Q⁶ is H, OH, SH, NH², C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆cycloalkylamino, halogen,

[0180] C₁₋₄ alkyl, C₁₋₄ alkoxy, or CF₃;

[0181] Q⁵ is H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆ alkynyl, C₁₋₄ alkylamino,CF₃, halogen, N, CN, NO₂, NHCONH₂, CONQ¹¹Q¹¹, CSNQ¹¹Q¹¹, COOQ¹¹,C(═NH)NH₂, hydroxy, C₁₋₃alkoxy, amino, C₁₋₄ alkylamino, di(C₁₋₄alkyl)amino, halogen, 1,3-oxazol-2-yl, 1,3-thiazol-2-yl, orimidazol-2-yl; wherein alkyl is unsubstituted or substituted with one tothree groups independently selected from halogen, amino, hydroxy,carboxy, and C₁₋₃ alkoxy;

[0182] Q⁷ and Q¹⁴ are each independently selected from the groupconsisting of H, CF₃, OH, SH, OR, SR C₁₋₄ alkyl, amino, C₁₋₄ alkylamino,C₃₋₆ cycloalkylamino, and di(C₁₋₄ alkyl)amino;

[0183] Q¹¹ is independently H or C₁₋₆ alkyl;

[0184] Q⁸ is H, halogen, CN, carboxy, C₁₋₄ alkyloxycarbonyl, N₃, amino,C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, hydroxy, C₁₋₆ alkoxy, C₁₋₆alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)0-2 aminomethyl, N, CN, NO₂,C₁₋₃ alkyl, NHCONH₂, CONQ¹¹Q¹¹, CSNQ¹¹Q¹¹, COOQ¹¹, C(═NH)NH₂,1,3-oxazol-2-yl, 1,3-thiazol-2-yl, or imidazol-2-yl, wherein alkyl isunsubstituted or substituted with one to three groups independentlyselected from halogen, amino, hydroxy, carboxy, and C₁₋₃ alkoxy;

[0185] wherein:

[0186] T₁ and T₂ are independently selected from N, CH, or C—Q¹⁶;

[0187] Q¹⁶, U, and Y are independently selected from is H, OH,substituted or unsubstituted alkyl, substituted or unsubstitutedalkenyl, substituted or unsubstituted alkynyl, cycloalkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵,Br-vinyl, —O-alkyl, —O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl,—O-acyl, —O-cycloalkyl, NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl,N-aralkyl, NH-cycloalkyl, SH, S-alkyl, S-acyl, S-aryl, S-cycloalkyl,S-aralkyl, CN, N₃, COOH, CONH₂, CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH,CF₃, CH₂OH, (CH₂)_(m)OH, (CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN,(CH₂)_(m)NO₂, (CH₂)_(m)CONH₂, C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆cycloalkylamino, C₁₋₄ alkoxy, C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂ aminomethyl, or —NHC(═NH)NH₂;

[0188] R⁴ and R⁵ are independently selected from hydrogen, acyl(including lower acyl), or alkyl (including but not limited to methyl,ethyl, propyl and cyclopropyl);

[0189] m is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10;

[0190] Z is S, SO, SO₂, C═O, or NQ²⁰;

[0191] Q²⁰ is H or alkyl; and

[0192] V₁ and V₂ are independently selected from CH or N;

[0193] wherein:

[0194] T₃ and T₄ are independently selected from N or CQ²²;

[0195] Q²² is independently selected from H, OH, substituted orunsubstituted alkyl, substituted or unsubstituted alkenyl, substitutedor unsubstituted alkynyl, cycloalkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵, Br-vinyl, —O-alkyl,—O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl, —O-acyl, —O-cycloalkyl,NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl, N-aralkyl, NH-cycloalkyl, SH,S-alkyl, S-acyl, S-aryl, S-cycloalkyl, S-aralkyl, CN, N₃, COOH, CONH₂,CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH, CF₃, CH₂OH, (CH₂)_(m)OH,(CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN, (CH₂)_(m)NO₂, (CH₂)_(m)CONH₂,C₁₋₄ alkylamino, di(C₁₋₄alkyl)amino, C₃₋₆ cycloalkylamino, C₁₋₄ alkoxy,C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂aminomethyl, or —NHC(═NH)NH₂;

[0196] R⁴ and R⁵ are independently selected from hydrogen, acyl(including lower acyl), or alkyl (including but not limited to methyl,ethyl, propyl and cyclopropyl);

[0197] m is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10;

[0198] T₆, T₇, T₈, T₉, T₁₀, T₁₁, and T₁₂ are independently selected fromN or CH;

[0199] U₂ is H, straight chained, branched or cyclic alkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵;

[0200] Y₂ is O, S, NH, NR or CQ²⁴Q²⁶ where R is H, OH, or alkyl;

[0201] Q²⁴ and Q²⁶ are independently selected from H, alkyl, straightchained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵;

[0202] Further examples of purine bases include, but are not limited to,guanine, adenine, hypoxanthine, 2,6-diaminopurine, and 6-chloropurine.Functional oxygen and nitrogen groups on the base can be protected asnecessary or desired. Suitable protecting groups are well known to thoseskilled in the art, and include trimethylsilyl, dimethylhexylsilyl,t-butyldimethylsilyl, and t-butyldiphenylsilyl, trityl, alkyl groups,and acyl groups such as acetyl and propionyl, methanesulfonyl, andp-toluenesulfonyl.

[0203] The term acyl refers to a carboxylic acid ester in which thenon-carbonyl moiety of the ester group is selected from straight,branched, or cyclic alkyl or lower alkyl, optionally substituted amido,alkoxyalkyl including methoxymethyl, aralkyl including benzyl,aryloxyalkyl such as phenoxymethyl, aryl including phenyl optionallysubstituted with chloro, bromo, fluoro, iodo, C₁ to C₄ alkyl or C₁ to C₄alkoxy, sulfonate esters such as alkyl or aralkyl sulphonyl includingmethanesulfonyl, the mono, di or triphosphate ester, trityl ormonomethoxytrityl, substituted benzyl, trialkylsilyl (e.g.dimethyl-t-butylsilyl) or diphenylmethylsilyl. Aryl groups in the estersoptimally comprise a phenyl group. The term “lower acyl” refers to anacyl group in which the non-carbonyl moiety is a lower alkyl.

[0204] As used herein, the term “substantially free of” or“substantially in the absence of” refers to a nucleoside compositionthat includes at least 95% to 98% by weight, and even more preferably99% to 100% by weight, of the designated enantiomer of that nucleoside.In a preferred embodiment, in the methods and compounds of thisinvention, the compounds are substantially free of enantiomers.

[0205] Similarly, the term “isolated” refers to a nucleoside compositionthat includes at least 95% to 98% by weight, and even more preferably99% to 100% by weight, of the nucleoside, the remainder comprising otherchemical species or enantiomers.

[0206] The term “independently” is used herein to indicate that thevariable which is independently applied varies independently fromapplication to application. Thus, in a compound such as R″XYR″, whereinR″ is “independently carbon or nitrogen,” both R″ can be carbon, both R″can be nitrogen, or one R″ can be carbon and the other R″ nitrogen.

[0207] The term host, as used herein, refers to an unicellular ormulticellular organism in which the virus can replicate, including celllines and animals, and preferably a human. Alternatively, the host canbe carrying a part of the hepatitis C viral genome, whose replication orfunction can be altered by the compounds of the present invention. Theterm host specifically refers to infected cells, cells transfected withall or part of the HCV genome and animals, in particular, primates(including chimpanzees) and humans. In most animal applications of thepresent invention, the host is a human patient. Veterinary applications,in certain indications, however, are included in the present invention(such as chimpanzees).

[0208] The term “pharmaceutically acceptable salt or prodrug” is usedthroughout the specification to describe any pharmaceutically acceptableform (such as an ester, phosphate ester, salt of an ester or a relatedgroup) of a nucleoside compound which, upon administration to a patient,provides the nucleoside compound. Pharmaceutically acceptable saltsinclude those derived from pharmaceutically acceptable inorganic ororganic bases and acids. Suitable salts include those derived fromalkali metals such as potassium and sodium, alkaline earth metals suchas calcium and magnesium, among numerous other acids well known in thepharmaceutical art. Pharmaceutically acceptable prodrugs refer to acompound that is metabolized, for example hydrolyzed or oxidized, in thehost to form the compound of the present invention. Typical examples ofprodrugs include compounds that have biologically labile protectinggroups on a functional moiety of the active compound. Prodrugs includecompounds that can be oxidized, reduced, aminated, deaminated,hydroxylated, dehydroxylated, hydrolyzed, dehydrolyzed, alkylated,dealkylated, acylated, deacylated, phosphorylated, dephosphorylated toproduce the active compound. The compounds of this invention possessantiviral activity against HCV, or are metabolized to a compound thatexhibits such activity.

[0209] III. Nucleotide Salt or Prodrug Formulations

[0210] In cases where compounds are sufficiently basic or acidic to formstable nontoxic acid or base salts, administration of the compound as apharmaceutically acceptable salt may be appropriate. Examples ofpharmaceutically acceptable salts are organic acid addition salts formedwith acids, which form a physiological acceptable anion, for example,tosylate, methanesulfonate, acetate, citrate, malonate, tartarate,succinate, benzoate, ascorbate, α-ketoglutarate, and α-glycerophosphate.Suitable inorganic salts may also be formed, including, sulfate,nitrate, bicarbonate, and carbonate salts.

[0211] Pharmaceutically acceptable salts may be obtained using standardprocedures well known in the art, for example by reacting a sufficientlybasic compound such as an amine with a suitable acid affording aphysiologically acceptable anion. Alkali metal (for example, sodium,potassium or lithium) or alkaline earth metal (for example calcium)salts of carboxylic acids can also be made.

[0212] Any of the nucleosides described herein can be administered as anucleotide prodrug to increase the activity, bioavailability, stabilityor otherwise alter the properties of the nucleoside. A number ofnucleotide prodrug ligands are known. In general, alkylation, acylationor other lipophilic modification of the mono, di or triphosphate of thenucleoside will increase the stability of the nucleotide. Examples ofsubstituent groups that can replace one or more hydrogens on thephosphate moiety are alkyl, aryl, steroids, carbohydrates, includingsugars, 1,2-diacylglycerol and alcohols. Many are described in R. Jonesand N. Bischofberger, Antiviral Research, 27 (1995) 1-17. Any of thesecan be used in combination with the disclosed nucleosides to achieve adesired effect.

[0213] The active nucleoside can also be provided as a 5′-phosphoetherlipid or a 5′-ether lipid, as disclosed in the following references,which are incorporated by reference herein: Kucera, L. S., N. Iyer, E.Leake, A. Raben, Modest E. K., D. L. W., and C. Piantadosi. 1990. “Novelmembrane-interactive ether lipid analogs that inhibit infectious HIV-1production and induce defective virus formation.” AIDS Res. Hum. RetroViruses. 6:491-501; Piantadosi, C., J. Marasco C. J., S. L.Morris-Natschke, K. L. Meyer, F. Gumus, J. R. Surles, K. S. Ishaq, L. S.Kucera, N. Iyer, C. A. Wallen, S. Piantadosi, and E. J. Modest. 1991.“Synthesis and evaluation of novel ether lipid nucleoside conjugates foranti-HIV activity.” J. Med. Chem. 34:1408.1414; Hosteller, K. Y., D. D.Richman, D. A. Carson, L. M. Stuhmiller, G. M. T. van Wijk, and H. vanden Bosch. 1992. “Greatly enhanced inhibition of human immunodeficiencyvirus type 1 replication in CEM and HT4-6C cells by 3′-deoxythymidinediphosphate dimyristoylglycerol, a lipid prodrug of 3,-deoxythymidine.”Antimicrob. Agents Chemother. 36:2025.2029; Hosetler, K. Y., L. M.Stuhmiller, H. B. Lenting, H. van den Bosch, and D. D. Richman, 1990.“Synthesis and antiretroviral activity of phospholipid analogs ofazidothymidine and other antiviral nucleosides.” J. Biol. Chem.265:61127.

[0214] Nonlimiting examples of U.S. patents that disclose suitablelipophilic substituents that can be covalently incorporated into thenucleoside, preferably at the 5′-OH position of the nucleoside orlipophilic preparations, include U.S. Pat. Nos. 5,149,794 (Sep. 22,1992, Yatvin et al.); 5,194,654 (Mar. 16, 1993, Hostetler et al.,5,223,263 (Jun. 29, 1993, Hostetler et al.); 5,256,641 (Oct. 26, 1993,Yatvin et al.); 5,411,947 (May 2, 1995, Hostetler et al.); 5,463,092(Oct. 31, 1995, Hostetler et al.); 5,543,389 (Aug. 6, 1996, Yatvin etal.); 5,543,390 (Aug. 6, 1996, Yatvin et al.); 5,543,391 (Aug. 6, 1996,Yatvin et al.); and 5,554,728 (Sep. 10, 1996; Basava et al.), all ofwhich are incorporated herein by reference. Foreign patent applicationsthat disclose lipophilic substituents that can be attached to thenucleosides of the present invention, or lipophilic preparations,include WO 89/02733, WO 90/00555, WO 91/16920, WO 91/18914, WO 93/00910,WO 94/26273, WO 96/15132, EP 0 350 287, EP 93917054.4, and WO 91/19721.

[0215] IV. Combination and Alternation Therapy

[0216] It has been recognized that drug-resistant variants of HCV canemerge after prolonged treatment with an antiviral agent. Drugresistance most typically occurs by mutation of a gene that encodes foran enzyme used in viral replication. The efficacy of a drug against HCVinfection can be prolonged, augmented, or restored by administering thecompound in combination or alternation with a second, and perhaps third,antiviral compound that induces a different mutation from that caused bythe principle drug. Alternatively, the pharmacokinetics, biodistributionor other parameter of the drug can be altered by such combination oralternation therapy. In general, combination therapy is typicallypreferred over alternation therapy because it induces multiplesimultaneous stresses on the virus.

[0217] Any of the HCV treatments described in the Background of theInvention can be used in combination or alternation with the compoundsdescribed in this specification. Nonlimiting examples include:

[0218] (1) an interferon and/or ribavirin (Battaglia, A. M. et al., Ann.Pharmacother. 34:487-494, 2000); Berenguer, M. et al. Antivir. Ther.3(Suppl. 3):125-136, 1998);

[0219] (2) Substrate-based NS3 protease inhibitors (Attwood et al.,Antiviral peptide derivatives, PCT WO 98/22496, 1998; Attwood et al.,Antiviral Chemistry and Chemotherapy 10.259-273, 1999; Attwood et al.,Preparation and use of amino acid derivatives as anti-viral agents,German Patent Publication DE 19914474; Tung et al. Inhibitors of serineproteases, particularly hepatitis C virus NS3 protease, PCT WO98/17679), including alphaketoamides and hydrazinoureas, and inhibitorsthat terminate in an electrophile such as a boronic acid or phosphonate.Llinas-Brunet et al, Hepatitis C inhibitor peptide analogues, PCT WO99/07734.

[0220] (3) Non-substrate-based inhibitors such as2,4,6-trihydroxy-3-nitro-benzamide derivatives(Sudo K. et al.,Biochemical and Biophysical Research Communications, 238:643-647, 1997;Sudo K. et al. Antiviral Chemistry and Chemotherapy 9:186, 1998),including RD3-4082 and RD3-4078, the former substituted on the amidewith a 14 carbon chain and the latter processing a para-phenoxyphenylgroup;

[0221] (4) Thiazolidine derivatives which show relevant inhibition in areverse-phase HPLC assay with an NS3/4A fusion protein and NS5A/5Bsubstrate (Sudo K. et al., Antiviral Research 32:9-18, 1996), especiallycompound RD-1-6250, possessing a fused cinnamoyl moiety substituted witha long alkyl chain, RD4 6205 and RD4 6193;

[0222] (5) Thiazolidines and benzanilides identified in Kakiuchi N. etal. J. EBS Letters 421:217-220; Takeshita N. et al. AnalyticalBiochemistry 247:242-246, 1997;

[0223] (6) A phenanthrenequinone possessing activity against HCVprotease in a SDS-PAGE and autoradiography assay isolated from thefermentation culture broth of Streptomyces sp., Sch 68631 (Chu M. etal., Tetrahedron Letters 37:7229-7232, 1996), and Sch 351633, isolatedfrom the fungus Penicillium griscofuluum, which demonstrates activity ina scintillation proximity assay (Chu M. et al., Bioorganic and MedicinalChemistry Letters 9:1949-1952);

[0224] (7) Selective NS3 inhibitors based on the macromolecule elgin c,isolated from leech (Qasim M. A. et al., Biochemistry 36:1598-1607,1997);

[0225] (8) HCV helicase inhibitors (Diana G. D. et al., Compounds,compositions and methods for treatment of hepatitis C, U.S. Pat. No.5,633,358; Diana G. D. et al., Piperidine derivatives, pharmaceuticalcompositions thereof and their use in the treatment of hepatitis C, PCTWO 97/36554);

[0226] (9) HCV polymerase inhibitors such as nucleotide analogues,gliotoxin (Ferrari R. et al. Journal of Virology 73:1649-1654, 1999),and the natural product cerulenin (Lohmann V. et al., Virology249:108-118, 1998);

[0227] (10) Antisense phosphorothioate oligodeoxynucleotides (S-ODN)complementary to sequence stretches in the 5′ non-coding region (NCR) ofthe HCV (Alt M. et al., Hepatology 22:707-717, 1995), or nucleotides326-348 comprising the 3′ end of the NCR and nucleotides 371-388 locatedin the core coding region of the IICV RNA (Alt M. et al., Archives ofVirology 142:589-599, 1997; Galderisi U. et al., Journal of CellularPhysiology 181:251-257, 1999);

[0228] (11) Inhibitors of IRES-dependent translation (Ikeda N et al.,Agent for the prevention and treatment of hepatitis C, Japanese PatentPublication JP-08268890; Kai Y. et al. Prevention and treatment of viraldiseases, Japanese Patent Publication JP-10101591);

[0229] (12) Nuclease-resistant ribozymes. (Maccjak D. J. et al.,Hepatology 30 abstract 995, 1999); and

[0230] (13) Other miscellaneous compounds including1-amino-alkylcyclohexanes (U.S. Pat. No. 6,034,134 to Gold et al.),alkyl lipids (U.S. Pat. No. 5,922,757 to Chojkier et al.), vitamin E andother antioxidants (U.S. Pat. No. 5,922,757 to Chojkier et al.),squalene, amantadine, bile acids (U.S. Pat. No. 5,846,964 to Ozeki etal.), N-(phosphonoacetyl)-L-aspartic acid, (U.S. Pat. No. 5,830,905 toDiana et al.), benzenedicarboxamides (U.S. Pat. No. 5,633,388 to Dianaet al.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wanget al.), 2′,3′-dideoxylnosine (U.S. Pat. No. 5,026,687 to Yarchoan etal.), and benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.);and

[0231] (14) PEGASYS (pegylated interferon alfa-2a) by Roche, INFERGEN(interferon alfacon-1) by InterMune, OMNIFERON (natural interferon) byViragen, ALBUFERON by Human Genome Sciences, REBIF (interferon beta-1a)by Ares-Serono, Omega Interferon by BioMedicine, Oral Interferon Alphaby Amarillo Biosciences, Interferon gamma-1b by InterMune,Interleukin-10 by Schering-Plough, IP-501 by Interneuron, MerimebodibVX-497 by Vertex, AMANTADINE (Symmetrel) by Endo Labs Solvay, HEPTAZYMEby RPI, IDN-6556 by Idun Pharma., XTL-002 by XTL., HCV/MF59 by Chiron,CIVACIR by NABI, LEVOVIRIN by ICN, VIRAMIDINE by ICN, ZADAXIN (thymosinalfa-1) by Sci Clone, CEPLENE (histamine dihydrochloride) by Maxim, VX950/LY 570310 by Vertex/Eli Lilly, ISIS 14803 by IsisPharmaceutical/Elan, IDN-6556 by Idun Pharmaceuticals, Inc. and JTK 003by AKROS Pharma..

[0232] V. Pharmaceutical Compositions

[0233] Hosts, including humans, infected with HCV or another organismreplicating through a RNA-dependent RNA viral polymerase, can be treatedby administering to the patient an effective amount of the activecompound or a pharmaceutically acceptable prodrug or salt thereof in thepresence of a pharmaceutically acceptable carrier or diluent. The activematerials can be administered by any appropriate route, for example,orally, parenterally, intravenously, intradermally, subcutaneously, ortopically, in liquid or solid form.

[0234] A preferred dose of the compound for HCV will be in the rangefrom about 1 to 50 mg/kg, preferably 1 to 20 mg/kg, of body weight perday, more generally 0.1 to about 100 mg per kilogram body weight of therecipient per day. The effective dosage range of the pharmaceuticallyacceptable salts and prodrugs can be calculated based on the weight ofthe parent nucleoside to be delivered. If the salt or prodrug exhibitsactivity in itself, the effective dosage can be estimated as above usingthe weight of the salt or prodrug, or by other means known to thoseskilled in the art.

[0235] The compound is conveniently administered in unit any suitabledosage form, including but not limited to one containing 7 to 3000 mg,preferably 70 to 1400 mg of active ingredient per unit dosage form. Aoral dosage of 50-1000 mg is usually convenient.

[0236] Ideally the active ingredient should be administered to achievepeak plasma concentrations of the active compound of from about 0.2 to70 μM, preferably about 1.0 to 10 μM. This may be achieved, for example,by the intravenous injection of a 0.1 to 5% solution of the activeingredient, optionally in saline, or administered as a bolus of theactive ingredient.

[0237] The concentration of active compound in the drug composition willdepend on absorption, inactivation and excretion rates of the drug aswell as other factors known to those of skill in the art. It is to benoted that dosage values will also vary with the severity of thecondition to be alleviated. It is to be further understood that for anyparticular subject, specific dosage regimens should be adjusted overtime according to the individual need and the professional judgment ofthe person administering or supervising the administration of thecompositions, and that the concentration ranges set forth herein areexemplary only and are not intended to limit the scope or practice ofthe claimed composition. The active ingredient may be administered atonce, or may be divided into a number of smaller doses to beadministered at varying intervals of time.

[0238] A preferred mode of administration of the active compound isoral. Oral compositions will generally include an inert diluent or anedible carrier. They may be enclosed in gelatin capsules or compressedinto tablets. For the purpose of oral therapeutic administration, theactive compound can be incorporated with excipients and used in the formof tablets, troches, or capsules. Pharmaceutically compatible bindingagents, and/or adjuvant materials can be included as part of thecomposition.

[0239] The tablets, pills, capsules, troches and the like can containany of the following ingredients, or compounds of a similar nature: abinder such as microcrystalline cellulose, gum tragacanth or gelatin; anexcipient such as starch or lactose, a disintegrating agent such asalginic acid, Primogel, or corn starch; a lubricant such as magnesiumstearate or Sterotes; a glidant such as colloidal silicon dioxide; asweetening agent such as sucrose or saccharin; or a flavoring agent suchas peppermint, methyl salicylate, or orange flavoring. When the dosageunit form is a capsule, it can contain, in addition to material of theabove type, a liquid carrier such as a fatty oil. In addition, dosageunit forms can contain various other materials which modify the physicalform of the dosage unit, for example, coatings of sugar, shellac, orother enteric agents.

[0240] The compound can be administered as a component of an elixir,suspension, syrup, wafer, chewing gum or the like. A syrup may contain,in addition to the active compounds, sucrose as a sweetening agent andcertain preservatives, dyes and colorings and flavors.

[0241] The compound or a pharmaceutically acceptable prodrug or saltsthereof can also be mixed with other active materials that do not impairthe desired action, or with materials that supplement the desiredaction, such as antibiotics, antifungals, anti-inflammatories, or otherantivirals, including other nucleoside compounds. Solutions orsuspensions used for parenteral, intradermal, subcutaneous, or topicalapplication can include the following components: a sterile diluent suchas water for injection, saline solution, fixed oils, polyethyleneglycols, glycerine, propylene glycol or other synthetic solvents;antibacterial agents such as benzyl alcohol or methyl parabens;antioxidants such as ascorbic acid or sodium bisulfite; chelating agentssuch as ethylenediaminetetraacetic acid; buffers such as acetates,citrates or phosphates and agents for the adjustment of tonicity such assodium chloride or dextrose. The parental preparation can be enclosed inampoules, disposable syringes or multiple dose vials made of glass orplastic.

[0242] If administered intravenously, preferred carriers arephysiological saline or phosphate buffered saline (PBS).

[0243] In a preferred embodiment, the active compounds are prepared withcarriers that will protect the compound against rapid elimination fromthe body, such as a controlled release formulation, including implantsand microencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters and polylactic acid.Methods for preparation of such formulations will be apparent to thoseskilled in the art. The materials can also be obtained commercially fromAlza Corporation.

[0244] Liposomal suspensions (including liposomes targeted to infectedcells with monoclonal antibodies to viral antigens) are also preferredas pharmaceutically acceptable carriers. These may be prepared accordingto methods known to those skilled in the art, for example, as describedin U.S. Pat. No. 4,522,811 (which is incorporated herein by reference inits entirety). For example, liposome formulations may be prepared bydissolving appropriate lipid(s) (such as stearoyl phosphatidylethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidylcholine, and cholesterol) in an inorganic solvent that is thenevaporated, leaving behind a thin film of dried lipid on the surface ofthe container. An aqueous solution of the active compound or itsmonophosphate, diphosphate, and/or triphosphate derivatives is thenintroduced into the container. The container is then swirled by hand tofree lipid material from the sides of the container and to disperselipid aggregates, thereby forming the liposomal suspension.

[0245] VI. Processes for the Preparation of Active Compounds

[0246] The nucleosides of the present invention can be synthesized byany means known in the art. In particular, the synthesis of the presentnucleosides can be achieved by either alkylating the appropriatelymodified sugar, followed by glycosylation or glycosylation followed byalkylation of the nucleoside, though preferably alkylating theappropriately modified sugar, followed by glycosylation. The followingnon-limiting embodiments illustrate some general methodology to obtainthe nucleosides of the present invention.

[0247] General Synthesis of 4′-C-Branched Nucleosicles

[0248] 4′-C-Branched ribonucleosides of the following structure:

[0249] wherein BASE is a purine or pyrimidine base as defined herein;

[0250] R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl(including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,—C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl),—O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂;

[0251] R⁸ and R¹⁰ are independently H, alkyl (including lower alkyl),chlorine, bromine or iodine;

[0252] alternatively, R⁷ and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰can come together to form a pi bond;

[0253] R¹ and R² are independently H; phosphate (includingmonophosphate, diphosphate, triphosphate, or a stabilized phosphateprodrug); acyl (including lower acyl); alkyl (including lower alkyl);sulfonate ester including alkyl or arylalkyl sulfonyl includingmethanesulfonyl and benzyl, wherein the phenyl group is optionallysubstituted with one or more substituents as described in the definitionof aryl given herein; a lipid, including a phospholipid; an amino acid;a carbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹ is independently H or phosphate;

[0254] R⁶ is an alkyl, halogeno-alkyl (i.e. CF₃), alkenyl, or alkynyl(i.e. allyl); and

[0255] X is OS, SO₂ or CH₂

[0256] can be prepared by the following general method.

[0257] Modification from the Pentodialdo-furanose

[0258] The key starting material for this process is an appropriatelysubstituted pentodialdo-furanose. The pentodialdo-furanose can bepurchased or can be prepared by any known means including standardepimerization, substitution and cyclization techniques.

[0259] In a preferred embodiment, the pentodialdo-furanose is preparedfrom the appropriately substituted hexose. The hexose can be purchasedor can be prepared by any known means including standard epimerization(e.g. via alkaline treatment), substitution and coupling techniques. Thehexose can be either in the furanose form, or cyclized via any meansknown in the art, such as methodology taught by Townsend Chemistry ofNucleosides and Nucleotides, Plenum Press, 1994, preferably byselectively protecting the hexose, to give the appropriate hexafuranose.

[0260] The 4′-hydroxymethylene of the hexafuranose then can be oxidizedwith the appropriate oxidizing agent in a compatible solvent at asuitable temperature to yield the 4′-aldo-modified sugar. Possibleoxidizing agents are Swern reagents, Jones reagent (a mixture of chromicacid and sulfuric acid), Collins's reagent (dipyridine Cr(VI) oxide,Corey's reagent (pyridinium chlorochromate), pyridinium dichromate, aciddichromate, potassium permanganate, MnO₂, ruthenium tetroxide, phasetransfer catalysts such as chromic acid or permanganate supported on apolymer, Cl₂-pyridine, H₂O₂-ammonium molybdate, NaBrO₂—CAN, NaOCl inHOAc, copper chromite, copper oxide, Raney nickel, palladium acetate,Meerwin-Pondorf-Verley reagent (aluminum t-butoxide with another ketone)and N-bromosuccinimide, though preferably using H₃PO₄, DMSO and DCC in amixture of benzene/pyridine at room temperature.

[0261] Then, the pentodialdo-furanose can be optionally protected with asuitable protecting group, preferably with an acyl or silyl group, bymethods well known to those skilled in the art, as taught by Greene etal. Protective Groups in Organic Synthesis, John Wiley and Sons, SecondEdition, 1991. In the presence of a base, such as sodium hydroxide, theprotected pentodialdo-furanose can then be coupled with a suitableelectrophilic alkyl, halogeno-alkyl (i.e. CF₃), alkenyl or alkynyl (i.e.allyl), to obtain the 4′-alkylated sugar. Alternatively, the protectedpentodialdo-furanose can be coupled with the corresponding carbonyl,such as formaldehyde, in the presence of a base, such as sodiumhydroxide, with the appropriate polar solvent, such as dioxane, at asuitable temperature, which can then be reduced with an appropriatereducing agent to give the 4′-alkylated sugar. In one embodiment, thereduction is carried out using PhOC(S)Cl, DMAP, preferably inacetonitrile at room temperature, followed by treatment of ACCN and TMSSrefluxed in toluene.

[0262] The optionally activated sugar can then be coupled to the BASE bymethods well known to those skilled in the art, as taught by TownsendChemistry of Nucleosides and Nucleotides, Plenum Press, 1994. Forexample, an acylated sugar can be coupled to a silylated base with alewis acid, such as tin tetrachloride, titanium tetrachloride ortrimethylsilyltriflate in the appropriate solvent at a suitabletemperature.

[0263] Subsequently, the nucleoside can be deprotected by methods wellknown to those skilled in the art, as taught by Greene et al. ProtectiveGroups in Organic Synthesis, John Wiley and Sons, Second Edition, 1991.

[0264] In a particular embodiment, the 4′-C-branched ribonucleoside isdesired. Alternatively, deoxyribo-nucleoside is desired. To obtain thesedeoxyribo-nucleosides, a formed ribo-nucleoside can optionally beprotected by methods well known to those skilled in the art, as taughtby Greene et al. Protective Groups in Organic Synthesis, John Wiley andSons, Second Edition, 1991, and then the 2′-OH can be reduced with asuitable reducing agent. Optionally, the 2′-hydroxyl can be activated tofacilitate reduction; i.e. via the Barton reduction.

[0265] In another embodiment of the invention, the L-enantiomers aredesired. Therefore, the L-enantiomers can be corresponding to thecompounds of the invention can be prepared following the same foregoinggeneral methods, beginning with the corresponding L-pentodialdo-furanoseas starting material.

[0266] The present invention is described by way of illustration, in thefollowing examples. It will be understood by one of ordinary skill inthe art that these examples are in no way limiting and that variationsof detail can be made without departing from the spirit and scope of thepresent invention.

VII. EXAMPLES

[0267] Melting points were determined in open capillary tubes on a BüchiB-545 apparatus and are uncorrected. The UV absorption spectra wererecorded on an Uvikon XS spectrophotometer (99-9089). ¹H-NMR spectrawere run at room temperature in DMSO-d₆ or CDCl₃ with a Bruker AC 200,250 or 400 spectrometer. Chemical shifts are given in ppm, DMSO-d₆ orCDCl₃ being set at 2.49 or 7.26 ppm as reference. Deuterium exchange,decoupling experiments or 2D-COSY spectra were performed in order toconfirm proton assignments. Signal multiplicities are represented by s(singlet), d (doublet), dd (doublet of doublets), t (triplet), q(quadruplet), br (broad), mn (multiplet). All J-values are in Hz. FABmass spectra were recorded in the positive−(FAB>0) or negative−(FAB>0)ion mode on a JEOL JMS DX 300 mass spectrometer; the matrix was amixture (50:50, v/v) of glycerol and thioglycerol (GT). Thin layerchromatography was performed on precoated aluminum sheets of Silica Gel60 F₂₅₄ (Merck, Art. 5554), visualization of products being accomplishedby UV absorbency followed by charring with 10% ethanolic sulfuric acidand heating. Column chromatography was carried out on Silica Gel 60(Merck, Art. 9385) at atmospheric pressure.

Example 1 Preparation of1-O-Methyl-2,3-O-isopropylidene-β-D-ribofuranose (1)

[0268] The title compound can be prepared according to a publishedprocedure (Leonard, N. J.; Carraway, K. L. “5-Amino-5-deoxyribosederivatives. Synthesis and use in the preparation of “reversed”nucleosides” J. Heterocycl. Chem. 1966, 3, 485-489).

[0269] A solution of 50.0 g (0.34 mole) of dry D-ribose in 1.0 L ofacetone, 100 mL of 2,2-dimethoxypropane, 200 mL of methanol containing20 mL of methanol saturated with hydrogen chloride at 0° C. was stirredovernight at room temperature. The resulting solution was neutralizedwith pyridine and evaporated under reduced pressure. The resulting oilwas partitioned between 400 mL of water and 400 mL of methylenechloride. The water layer was extracted twice with methylene chloride(400 mL). The combined organic extracts were dried over sodium sulfateand evaporated under reduced pressure. The residue was purified bysilica gel column chromatography [cluent: stepwise gradient of methanol(1-2%) in methylene chloride] to give pure 1 (52.1 g, 75%) as a yellowsyrup. ¹H-NMR (CDCl₃): δ5.00 (s, 1H, H-1), 4.86 (d, 1H, H-2, J₂₋₃=5.9Hz), 4.61 (d, 1H, H-3, J₃₋₂=5.9 Hz), 4.46 (t, 1H, H-4, J₄₋₅=2.7 Hz),3.77-3.61 (m, 2H, H-5 and H-5′), 3.46 (s, 1H, OCH₃), 3.0-2.4 (br s, 1H,OH-5), 1.51 (s, 3H CH₃), 1.34 (s, 3H CH₃); MS (matrix GT): FAB>0 m/z 173(M−OCH3)⁺.

Example 2 Preparation of1-O-Methyl-2,3-O-isopropylidene-β-D-pentodialdo-ribofuranose (2)

[0270] The title compound can be prepared according to a publishedprocedure (Jones, G. H.; Moffatt, J. G. Oxidation of carbohydrates bythe sulfoxide-carbodiimide and related methods. Oxidation withdicyclohexylcarbodiimide-DMSO, diisopropylcarbodiimide-DMSO, aceticanhydride-DMSO, and phosphorus pentoxide-DMSO: in Methods inCarbohydrate Chemistry; Whisler, R. L. and Moffatt, J. L. Eds; AcademicPress: New York, 1972; 315-322).

[0271] Compound 1 was co-evaporated twice with anhydrous pyridine.Dicyclohexylcarbodi-imide (DCC, 137.8 g, 0.67 mol) was added to asolution of 1 (68.2 g, 0.33 mole) in anhydrous benzene (670 mL), DMSO(500 mL) and pyridine (13.4 mL). To the resulting solution, cooled to 0°C., was added a solution of anhydrous crystalline orthophosphoric acid(16.4 g, 0.167 mmol) in anhydrous DMSO (30 mL). The mixture was stirredfor 1.5 hours at 0° C. and 18 hours at room temperature under argonatmosphere, diluted with ethyl acetate (1000 mL). A solution of oxalicacid dihydrate (63.1 g, 038 mol) in DMSO (30 mL) was added and thereaction mixture was stirred at room temperature during 1 hour and thenfiltered to eliminate precipitated dicyclohexylurea (DCU). The filtratewas concentrated to a volume of about 600 mL under reduced pressure andneutralized with a saturated aqueous sodium hydrogen carbonate solution(400 mL). Brine (200 mL) was added and the organic layer was extractedwith ethyl acetate (4×1000 mL). The combined organic layers wereconcentrated to a volume of about 2000 mL, washed with a saturatedaqueous sodium hydrogen carbonate solution (2×700 mL), and with brine(2×700 mL) before being dried over sodium sulfate and evaporated underreduced pressure. A small fraction of the crude residue was purified onsilica gel chromatography [eluent: chloroform/ethyl ether, 8:2] in orderto confirm the structure of 2 which was obtained as a pale yellow solid.¹H-NMR (CDCl₃): δ9.61 (s, 1H, H-5), 5.12 (s, 1H, H-1), 5.08 (d, 1H, H-2,J₂₋₃=5.9 Hz), 4.53 (d, 1H, H-3, J₃₋₂=6.0 Hz), 4.51 (s, 1H, H-4), 3.48(s, 1H, OCH₃), 1.56 (s, 3H CH₃), 1.36 (s, 3H CH₃); MS (matrix GT): FAB>0m/z 203 (M+H)⁺, 171 M−OCH₃)⁺.

Example 3 Preparation of4-C-Hydroxymethyl-1-O-methyl-2,3-O-isopropylidene-β-D-ribofuranose (3)

[0272] The title compound can be prepared according to a publishedprocedure (Leland, D. L.; Kotick, M. P. “Studies on4-C-(hydroxymethyl)pentofuranoses. Synthesis of9-[4-C-(hydroxymethyl)-a-L-threo-pentofuranosyl]adenine” Carbohydr. Res.1974, 38, C9-C11; Jones, G. H.; Taniguchi, M.; Tegg, D.; Moffatt, J. G.“4′-substituted nucleosides. 5. Hydroxylation of nucleoside5′-aldehydes” J. Org. Chem. 1979, 44, 1309-1317; Gunic, E.; Girardet,J.-L.; Pietrzkowski, Z.; Esler, C.; Wang, G. “Synthesis and cytotoxicityof 4′-C- and 5′-C-substituted Toyocamycins” Bioorg. Med. Chem. 2001, 9,163-170).

[0273] To a solution of the crude material (2) obtained above and 37%aqueous formaldehyde (167 mL) in dioxane (830 mL) was added aqueoussodium hydroxyde (2N, 300 mL). The mixture was stirred at roomtemperature for 4 hours and neutralized by addition of Dowex 50 W×2 (H⁺form). The resin was filtered, washed with methanol, and the combinedfiltrates were concentrated to dryness and coevaporated several timeswith absolute ethanol. Sodium formate which was precipitated fromabsolute ethanol was removed by filtration, the filtrate wasconcentrated to dryness and the residue was purified by silica gelcolumn chromatography [eluent: stepwise gradient of methanol (0-4%) inchloroform] to give pure 3 (42.2 g, 54% from 1), which wasrecrystallized from cyclohexane. Mp=94-95 (dec.) (lit.94-96.5; 97-98:Refs: 3,4), ¹H-NMR (DMSO-d₆): δ4.65 (s, 1H, H-1), 4.44-4.37 (m, 3H, H-2,H-3 and OH-6), 4.27 (t, 1H, OH-5, J=5.6 Hz, J=6.0 Hz), 3.42-3.34 (m, 2H,H-5 and H-6) 3.29 (dd, 1H, H-5′, J_(5′-OH)=5.4 Hz, J5-5′=11.4 Hz), 3.11(dd, 1H, H-6′, J_(6′-OH)=5.7 Hz, J6-6′=10.9 Hz), 3.03 (s, 3H, OCH₃),1.48 (s, 3H CH₃), 1.05 (s, 3H CH₃); MS (matrix GT): FAB>0 m/z 469(2M+H)⁺, 235 (M+H)⁺, 203 (M−OCH₃)+ FAB<0 m/z 233 (M−H)⁻.

Example 4 Preparation of6-O-Monomethoxytrityl-4-C-hydroxymethyl-1-O-methyl-2,3-O-isopropylidene-β-D-ribofuranose(4)

[0274] The title compound can be prepared according to a publishedprocedure (Gunic, E.; Girardet, J.-L.; Pietrzkowski, Z.; Esler, C.;Wang, G. “Synthesis and cytotoxicity of 4′-C- and 5′-C-substitutedToyocamycins” Bioorg. Med. Chem. 2001, 9, 163-170).

[0275] To a solution of 3 (41.0 g, 175 mmol) in pyridine (700 ml) wasadded by portions dimethoxytrityl chloride (60.5 g, 178 mmol) at +4° C.The reaction mixture was stirred for 3 hours at room temperature. Afteraddition of methanol, the reaction mixture was concentrated (200 ml) andthen dissolved with ethyl acetate (2 L). The organic layer was washedwith a 5% aqueous sodium hydrogen carbonate solution, with water anddried over sodium sulfate and then evaporated to dryness. Purificationby silica gel column chromatography [eluent: ethyl acetate/hexane 15/85]afforded pure 4 (63.0 g, 68%) as a syrup. ¹H-NMR (CDCl₃): δ7.5-6.9 (m,13H, MMTr), 4.89 (s, 1H, H-1), 4.72-4.62 (m, 3H, H-2, H-3 and OH-5),3.82 (dd, 1H, H-5, J_(5-OH)=5.5 Hz, J5-5′=10.5 Hz), 3.79 (s, 6H, OCH3),3.54 (dd, 1H, H-5′, J_(5′-OH)=4.9 Hz, J_(5′-5)=10.5 Hz), 3.31 (s, 3H,OCH₃), 3.24 (d, 1H, H-6, J_(6-6′)=9.2 Hz), 3.13 (d, 1H, H-6′,J_(6′-6)=9.2 Hz), 1.24 (s, 3H CH₃), 1.15 (s, 3H CH₃); MS (matrix GT):FAB>0 m/z 303 (DMTr)⁺.

Example 5 Preparation of5-O-Benzoyl-4-C-hydroxymethyl-1-O-methyl-2,3-O-isopropylidene-β-D-ribo-furanose(5)

[0276] The title compound can be prepared according to a publishedprocedure (Gunic, E.; Girardet, J.-L.; Pietrzkowski, Z.; Esler, C.;Wang, G. “Synthesis and cytotoxicity of 4′-C- and 5′-C-substitutedToyocamycins” Bioorg. Med. Chem. 2001, 9, 163-170).

[0277] To a solution of 4 (2.51 g, 4.68 mmol) in anhydrous pyridine (37mL) was added under argon benzoyl chloride (1.09 mL, 9.36 mmol) and thereaction mixture was stirred for 13 hours at to room temperature. Thenthe reaction was cooled to 0° C. and stopped with ice-cold water (100mL). The water layer was extracted with methylene chloride (3□ 200 mL).The combined organic layers were washed with a saturated aqueous sodiumhydrogen carbonate solution (2×150 mL), with water (1×150 mL) and thendried over sodium sulfate and evaporated under reduced pressure. Theresidue was dissolved in 80% acetic acid (70.2 mL) and the mixture wasstirred at room temperature for 3 hr and concentrated to dryness.Purification by silica gel column chromatography [eluent: chloroform]afforded pure 5 (1.40 g, 88%) as a syrup. ¹H-NMR (CDCl₃): δ8.1-7.4 (m,5H, C₆H₅CO), 5.08 (s, 1H, H-1), 4.77 (dd, 2H, H-2 and H-3, J=6.1 Hz,J=8.2 Hz), 4.51 (q, 2H, H-5 and H-5′, J=11.5 Hz, J_(5-5′)=23.8 Hz), 3.91(t, 2H, H-6 and H-6′, J=12.3 Hz), 4.38 (s, 1H, OCH₃), 2.2-1.8 (brs, 1H,OH-6), 1.57 (s, 3H CH₃), 1.38 (s, 3H CH₃); MS (matrix GT): FAB>0 m/z 677(2M+H)⁺, 339 (M+H)⁺, 307 (M−OCH₃)⁺, 105 (C₆H₅CO)⁺ FAB<0 m/z 121(C₆H₅CO₂)⁻.

Example 6 Preparation of5-O-Benzoyl-4-C-methyl-1-O-methyl-2,3-O-isopropylidene-β-D-ribofuranose(6)

[0278] The title compound can be prepared according to a publishedprocedure (Gunic, E.; Girardet, J.-L.; Pietrzkowski, Z.; Esler, C.;Wang, G. “Synthesis and cytotoxicity of 4′-C- and 5′-C-substitutedToyocamycins” Bioori. Med. Chem. 2001, 9, 163-170).

[0279] A solution of 5 (37.6 g, 0.111 mol), 4-dimethylaminopyridine(DMAP, 40.7 g, 0.333 mol) and phenoxythiocarbonyle chloride in anhydrousacetonitrile (1000 mL) was stirred at room temperature for 1 hour andconcentrated to dryness. The residue was dissolved in methylene chloride(500 mL) and successively washed with 0.2 M hydrochloric acid (2×500 mL)and water (500 mL) before being dried over sodium sulfate, evaporatedunder reduced pressure and coevaporated several times with anhydroustoluene. The crude material was dissolved in anhydrous toluene (880 mL)and tris(trimethylsilyl)silane (TMSS, 42.9 mL, 0.139 mol), and1,1′-azobis(cyclohexanecarbonitrile) (ACCN, 6.8 g, 27.8 mmol) wereadded. The reaction mixture was stirred under reflux for 45 minutes,cooled to room temperature and concentrated under reduced pressure. Theresulting residue was purified by silica gel column chromatography[eluent: stepwise gradient of diethyl ether (5-20%) in petroleum ether]to give pure 6 (26.4 g, 74%) as a pale yellow syrup. ¹H-NMR (DMSO-d₆):δ8.0-7.5 (m, 5H, C₆H₅CO), 4.85 (s, 1H, H-1), 4.63 (dd, 2H, H-2 and H-3,J=6.1 Hz, J=11.6 Hz), 4.24 (d, 1H, H-5, J_(5-5′)=11.1 Hz), 4.10 (d, 1H,H-5′, J_(5′-5)=11.1 Hz), 3.17 (s, 1H, OCH₃), 1.38 (s, 3H CH₃), 1.30 (s,3H CH₃), 1.25 (s, 3H CH₃); MS (matrix GT): FAB>0 m/z 291 (M−OCH₃)⁺, 105(C₆H₅CO)⁺ FAB<0 m/z 121 (C₆H₅CO₂)⁻.

Example 7 Preparation of5-O-Benzoyl-4-C-methyl-1,2,3-O-acetyl-α,β-D-ribofuranose (7)

[0280] Compound 6 (22.5 g, 70 mmol) was suspended in a 80% aqueousacetic acid solution (250 mL). The solution was heated at 100° C. for 3hours. The volume was then reduced by half and coevaporated withabsolute ethanol and pyridine. The oily residue was dissolved inpyridine (280 mL) and then cooled at 0° C. Acetic anhydride (80 mL) and4-dimethylamino-pyridine (500 mg) were added. The reaction mixture wasstirred at room temperature for 3 hours and then concentrated underreduced pressure. The residue was dissolved with ethyl acetate (1 L) andsuccessively washed with a saturated aqueous sodium hydrogen carbonatesolution, a 1 M hydrochloric acid and water. The organic layer was driedover sodium sulfate and evaporated under reduced pressure. The resultingresidue was purified by silica gel column chromatography [eluent:stepwise gradient of diethyl ether (30-40%) in petroleum ether] to givepure 7 (16.2 g, 60%) as a pale yellow syrup. A small fraction of thematerial was re-purified on silica gel chromatography [same eluent:system] in order separate the α and the β anomers.

[0281] α anomer: ¹H-NMR (DMSO-d₆): δ8.1-7.5 (m, 5H, C₆H₅CO), 6.34 (pt,1H, H-1, J=2.4 Hz, J=2.1 Hz), 5.49 (m, 2H, H-2 and H-3), 4.33 (q, 2H,H-5 and H-5′, J=11.6 Hz, J=18.7 Hz), 2.15 (s, 3H, CH₃CO₂), 2.11 (s, 3H,CH₃CO₂), 2.07 (S, 3H, CH₃CO₂), 1.37 (s, 3H, CH₃); MS (matrix GT): FAB>0m/z 335 (M−CH₃CO₂ ⁻)⁺, 275 (M−CH₃CO₂ ⁻+H)⁺,105 (C₆H₅CO)⁺, 43 (CH₃CO)⁺FAB<0 m/z 121 (C₆H₅CO₂)⁻, 59 (CH₃CO₂)⁻.

[0282] β anomer: ¹H-NMR (DMSO-d₆): δ8.1-7.5 (m, 5H, C₆H₅CO), 5.99 (s,1H, H-1), 5.46 (d, 1H, H-2, J₂₋₃=5.3 HZ), 5.30 (d, 1H, H-2, J₂₋₃=5.3Hz), 4.39 (d, 1H, H-5, J_(5-5′)=11.7 Hz), 4.19 (d, 1H, H-5′,J_(5′-5)=11.7 Hz), 2.10 (s, 3H, CH₃CO₂), 2.06 (s, 3H, CH₃CO₂), 2.02 (s,3H, CH₃CO₂), 1.30 (s, 3H, CH₃); MS (matrix GT): FAB>0 m/z 335 (M−CH₃CO₂⁻)⁺, 275 (M−CH₃CO₂ ⁻+H)⁺,105 (C₆H₅CO)⁺, 43 (CH₃CO)⁺ FAB<0 m/z 121(C₆H₅CO₂)⁻, 59 (CH₃CO₂)⁻.

Example 8 Preparation of1-(5-O-Benzoyl-4-C-methyl-2,3-O-acetyl-β-D-ribofuranosyl)uracil (8)

[0283] A suspension of uracil (422 mg, 3.76 mmol) was treated withhexamethyldisilazane (HMDS, 21 mL) and a catalytic amount of ammoniumsulfate during 17 hours under reflux. After cooling to room temperature,the mixture was evaporated under reduced pressure, and the residue,obtained as a colorless oil, was diluted with anhydrous1,2-dichloroethane (7.5 mL). To the resulting solution was added 7 (0.99g, 2.51 mmol) in anhydrous 1,2-dichloroethane (14 mL), followed byaddition of trimethylsilyl trifluoromethanesulfonate (TMSTf, 0.97 mL,5.02 mmol). The solution was stirred for 2.5 hours at room temperatureunder argon atmosphere, then diluted with chloroform (150 mL), washedwith the same volume of a saturated aqueous sodium hydrogen carbonatesolution and finally with water (2×100 mL). The organic phase was driedover sodium sulfate, then evaporated under reduced pressure. Theresulting crude material was purified by silica gel columnchromatography [eluent: stepwise gradient of methanol (0-2%) inchloroform] to afford pure 8 (1.07 g, 95%) as a foam. ¹H-NMR (DMSO-d6):δ11.48 (s, 1H, NH), 8.1-7.5 (m, 6H, C₆H₅CO and H-6), 5.94 (d, 1H, H-1′,J_(1′-2′)=3.3 Hz), 5.61 (m, 3H, H-5, H-2′ and H-3′), 4.47 (d, 1H, H-5′,J_(5′-5″)=11.7 Hz), 4.35 (d, 1H, H-5″, J_(5″-5′)=11.7 Hz), 2.12 (s, 3H,CH₃CO₂), 2.09 (s, 3H, CH₃CO₂), 1.38 (s, 3H, CH₃); MS (matrix GT): FAB>0m/z 893 (2M+H)⁺, 447 (M+H)⁺, 335 (S)⁺, 113 (BH₂)⁺, 105 (C₆H₅CO)⁺, 43(CH₃CO)⁺ FAB<0 m/z 891 (2M−H)⁻, 445 (M−H)⁻, 121 (C₆H₅CO₂)⁻, 111 (B)⁻, 59(CH₃CO₂)⁻.

Example 9 Preparation of 1-(4-C-methyl-β-D-ribofuranosyl)uracil (9)

[0284] The title compound can be prepared according to a publishedprocedure from 8 (Waga, T.; Nishizaki, T.; Miyakawa, I.; Orhui, H.;Meguro, H. “Synthesis of 4′-C-methylnucleosides” Biosci. Biotechnol.Biochem. 1993, 57, 1433-1438).

[0285] A solution of 8 (610 mg, 1.37 mmol) in methanolic ammonia(previously saturated at −10° C.) (27 mL) was stirred at roomtemperature overnight. The solvent was evaporated under reduced pressureand the residue was partitioned between methylene chloride (40 mL) andwater (40 mL). The aqueous layer was washed with methylene chloride(2×40 mL), concentrated under reduced pressure and coevaporated severaltimes with absolute ethanol. Recrystallization from a mixture absoluteethanol/methanol gave 9 (215 mg, 61%) as a colorless and crystallinesolid. Mp: 226-227 (dec.) (lit. 227: Ref.6); UV (H₂O): λ_(max)=259 nm(ε=10100), λ_(min)=228 nm (ε=2200); HPLC 99.56%, ¹H-NMR (DMSO-d₆):δ11.28 (s, 1H, NH), 7.89 (d, 1H, H-6, J₆₋₅=8.1 Hz), 5.80 (d, 1H, H-1′,J_(1′-2′)=7.1 Hz), 5.64 (d, 1H, H-5, J₅₋₆=8.1 Hz), 5.24 (d, 1H, OH-2′,J_(OH-2′)=6.5 Hz), 5.18 (t, 1H, OH-5′ J_(OH-5′)=J_(OH-5″)=5.2 Hz), 5.01(d, 1H, OH-3′, J_(OH-3′)=5.0 Hz), 4.28 (dd, 1H, H-2′, J=6.5 Hz, J=12.2Hz), 3.90 (t, 1H, H-3′, J_(3′-2′)=J_(3′-OH′)=5.1 Hz), 3.30 (m, 2H, H-5′and H-5″), 1.06 (s, 3H, CH₃); MS (matrix GT): FAB>0 m/z 517 (2M+H)⁺, 259(M+H)⁺, 147 (S)⁺ FAB<0 m/z 515 (2M−H)⁻, 257 (M−H)⁻.

Example 10 Preparation of1-(5-O-Benzoyl-4-C-methyl-2,3-O-acetyl-β-D-ribofuranosyl)4-thio-uracil(10)

[0286] Lawesson's reagent (926 mg, 2.29 mmol) was added under argon to asolution of 8 (1.46 g, 3.27 mmol) in anhydrous 1,2-dichloroethane (65mL) and the reaction mixture was stirred overnight under reflux. Thesolvent was evaporated under reduced pressure and the residue waspurified by silica gel column chromatography [eluent: stepwise gradientof methanol (1-2%) in chloroform] to give pure 10 (1.43 g, 95%) as ayellow foam. ¹H-NMR (DMSO-d₆): δ12.88 (s, 1H, NH), 8.1-7.5 (m, 6H,C₆H₅CO and H-6), 6.27 (d, 1H, H-1′, J_(1′-2′)=7.51 Hz), 5.91 (br s, 1H,H-5) 5.64 (m, 2H, H-2′ and H-3′), 4.47 (d, 1H, H-5′, J_(5′-5″)=11.7 Hz),4.36 (d, 1H, H-5′, J_(5′-5′)′=11.7 Hz), 2.11 (s, 3H, CH₃CO₂), 2.09 (s,3H, CH₃CO₂), 1.39 (s, 3H, CH₃); MS (matrix GT): FAB>0 nm/z 925 (2M+H)⁺,463 (M+H)⁺, 335 (S)⁺, 129 (BH₂)⁺, 105 (C₆H₅CO)⁺, 43 (CH₃CO)⁺ FAB<0 m/z461 (M−H)⁻, 127 (B)⁻, 121 (C₆H₅CO₂)⁻, 59 (CH₃CO₂)⁻.

Example 11 Preparation of 1-(4-C-methyl-β-D-ribofuranosyl)4-thio-uracil(11)

[0287] A solution of 10 (500 mg, 1.08 mmol) in methanolic ammonia(previously saturated at −10° C.) (27 mL) was stirred at roomtemperature overnight. The solvent was evaporated under reduced pressureand the residue was partitioned between methylene chloride (40 ml) andwater (40 mL). The aqueous layer was washed with methylene chloride(2×40 mL), concentrated under reduced pressure. The crude material waspurified by silica gel column chromatography [eluent: stepwise gradientof methanol (5-7%) in methylene chloride] to give pure 11 (188 mg, 63%),which was lyophilized. Mp: 65-70 (dec.); UV (methanol): λ_(max)=330 nm(ε=20000) 246 nm (ε=4200), λ_(min)=275 nm (ε=1500); ¹H-NMR (DMSO-d₆):δ12.51 (brs, 1H, NH), 7.81 (d, 1H, H-6, J₆₋₅=7.6 Hz), 6.30 (d, 1H, H-5,J₅₋₆=7.5 Hz), 5.77, (d, 1H, H-1′, J_(1′-2′)=6.7 Hz), 5.32 (d, 1H, OH-2′,J_(OH-2′)=6.1 Hz), 5.20 (t, 1H, OH-5′ J_(OH-5′)=J_(OH-5″)=5.2 Hz), 5.03(d, 1H, OH-3′, J_(OH-3′)=5.2 Hz), 4.17 (dd, 1H, H-2′, J=6.2 Hz, J=12.0Hz), 3.89 (t, 1H, H-3′, J_(3′-2′)=J_(3′-OH′)=5.1 Hz), 3.35 (m, 2H, H-5′and H-5″), 1.02 (s, 3H, CH₃); MS (matrix GT): FAB>0 m/z 275 (M+H)⁺, 147(S)⁺, 129(BH₂)⁺ FAB<0 m/z 547 (2M−H)⁻, 273 (M−H)⁻, 127 (B)⁻.

Example 12 Preparation of 1-(4-C-methyl-β-D-ribofuranosyl)cytosine,Hydrochloric Form (12)

[0288] Compound 11 (890 mg, 1.93 mmol) was treated with methanolicammonia (previously saturated at −10° C.), (12 mL) at 100° C. in astainless-steel bomb for 3 hours, then cooled to room temperature. Thesolvent was evaporated under reduced pressure and the residue waspartitioned between methylene chloride (40 mL) and water (40 mL). Theaqueous layer was washed with methylene chloride (2×40 mL), concentratedunder reduced pressure. The crude material was purified by silica gelcolumn chromatography [eluent: methylene chloride/methanol/ammoniumhydroxide 65:30:5]. The collected fractions were evaporated underreduced pressure and in absolute ethanol (6.3 mL). To the solution wasadded a 2N hydrochloric acid solution (1.5 mL) and the mixture wasstirred before being concentrated under reduced pressure. The procedurewas repeated twice and 12 was precipitated from absolute ethanol. Mp:213-214 (dec.); UV (methanol): λ_(max)=280 nm (ε=9800), λ_(min)=245 nm(ε=3600); ¹H-NMR (DMSO-d₆): δ9.82 (s, 1H, NH₂), 8.72 (s, 1H, NH₂), 8.34(d, 1H, H-6, J₆₋₅=7.8 Hz), 6.21 (d, 1H, H-5, J₅₋₆=7.8 Hz), 5.83 (d, 1H,H-1′, J_(1′-2′)=5.8 Hz), 4.22 (d, 1H, OH-2′, J_(OH-2′)=6.5 Hz), 5.6-4.7(m, 3H, OH-2′, OH-3′ and OH-5′), 4.28 (t, 1H, H-2′, J=5.6 Hz), 3.99 (d,1H, H-3′, J=5.3 Hz), 3.43 (m, 2H, H-5′ and H-5″), 1.14 (s, 3H, CH₃); MS(matrix GT): FAB>0 m/z 515 (2M+H)⁺, 258 (M+H)⁺, 147 (S)⁺, 112 (BH₂)⁺FAB<0 m/z 256 (M−H)⁻.

Example 13 Preparation of1-(5-O-Benzoyl-4-C-methyl-2,3-O-acetyl-β-D-ribofuranosyl)thymine (13)

[0289] A suspension of thymine (384 mg, 3.04 mmol) was treated withhexamethyldisilazane (HMDS, 17 mL) and a catalytic amount of ammoniumsulfate overnight under reflux. After cooling to room temperature, themixture was evaporated under reduced pressure, and the residue, obtainedas a colorless oil, was diluted with anhydrous 1,2-dichloroethane (6mL). To the resulting solution was added 7 (1.0 g, 2.53 mmol) inanhydrous 1,2-dichloroethane (14 mL), followed by addition oftrimethylsilyl trifluoromethanesulfonate (TMSTf, 0.98 mL, 5.06 mmol).The solution was stirred for 5 hours at room temperature under argonatmosphere, then diluted with chloroform (150 mL), washed with the samevolume of a saturated aqueous sodium hydrogen carbonate solution andfinally with water (2×100 mL). The organic phase was dried over sodiumsulfate, then evaporated under reduced pressure. The resulting crudematerial was purified by silica gel column chromatography [eluent: 2% ofmethanol in chloroform] to afford pure 13 (1.09 g, 94%) as a foam.¹H-NMR (DMSO-d₆): δ11.47 (s, 1H, NH), 8.1-7.4 (m, 6H, C₆H₅CO and H-6),5.98 (d, 1H, H-1′, J=5.0 Hz), 5.5-5.7 (m, 2H, H-2′ and H-3′), 4.42 (dd,2H, H-5′ and H-5″, J=11.6 Hz, J=31.6 Hz), 2.12 (s, 3H, CH₃CO₂), 2.09 (s,3H, CH₃CO₂), 1.60 (s, 1H, CH₃), 1.37 (s, 3H, CH₃); MS (matrix GT): FAB>0m/z 461 (M+H)⁺, 335 (S)⁺, 105 (C₆H₅CO)⁺, 43 (CH₃CO)⁺ FAB<0 m/z 459(M−H)⁻, 125 (B)⁻, 121 (C₆H₅CO₂)⁻, 59 (CH₃CO₂)⁻.

Example 14 Preparation of 1-(4-C-methyl-β-D-ribofuranosyl)thymine (14)

[0290] The title compound can be prepared according to a publishedprocedure from 13 (Waga, T.; Nishizaki, T.; Miyakawa, I.; Orhui, H.;Meguro, H. “Synthesis of 4′-C-methylnucleosides” Biosci. Biotechnol.Biochem. 1993, 57, 1433-1438).

[0291] A solution of 13 (1.09 g, 2.37 mmol) in methanolic ammonia(previously saturated at −10° C.) (60 mL) was stirred at roomtemperature overnight. The solvent was evaporated under reduced pressureand the residue was partitioned between methylene chloride (60 mL) andwater (60 mL). The aqueous layer was washed with methylene chloride(2×60 mL), concentrated under reduced pressure and coevaporated severaltimes with absolute ethanol. Recrystallization from methanol gave 14(450 mg, 70%) as a colorless and crystalline solid. Mp: 258-260 (dec.)(lit. 264: Ref.6); UV (H₂O): λ_(max)=264.4 nm (ε=8800), λ_(min)=232.0 nm(ε=2200); ¹H-NMR (DMSO-d₆): δ11.29 (s, 1H, NH), 7.75 (s, 1H, H-6), 5.82(d, 1H, H-1′, J_(1′-2′)=7.2 Hz), 5.19 (m, 2H, OH-2′, OH-5′), 5.02 (d,1H, OH-3′, J_(OH-3′)=5.0 Hz), 4.21 (dd, 1H, H-2′, J=6.4 Hz, J=12.3 Hz),3.92 (t, 1H, H-3′, J_(3′-2′)=J_(3′-OH′)=5.0 Hz), 3.30 (m, 2H, H-5′ andH-5″), 1.78 (s, 3H, CH₃), 1.09 (s, 3H, CH₃); MS (matrix GT): FAB>0 m/z545 (2M+H)⁺, 365 (M+G+H)⁺, 273 (M+H)⁺, 147 (S)⁺, 127 (B+2H)⁺, FAB<0 m/z543 (2M−H)⁻, 271 (M−H)⁻, 125 (B)⁻, [α]_(D) ²⁰−32.0 (c=0.5 in H₂O, litt.−26.4).

Example 15 Preparation of1-(5,2,3-Tri-O-acetyl-4-C-methyl-β-D-ribofuranosyl)thymine (15)

[0292] A solution of 14 (200 mg, 0.735 mmol) in anhydrous pyridine (7.4ml) was treated with acetic anhydride (1.2 mL) and stirred at roomtemperature for 3 hours. The solvent was evaporated under reducedpressure, and the residue was purified by silica gel columnchromatography [eluent: stepwise gradient of methanol (0-5%) inmethylene chloride] to afford pure 15 (0.400 g, quantitative yield) as afoam. ¹H-NMR (DMSO-d₆): δ11.45 (s, 1H, NH), 7.56 (s, 1H, H-6), 5.90 (d,1H, H-1′, J_(1′-2′)=4.8 Hz), 5.5-5.4 (m, 2H, H-2′ and H-3′), 4.3-4.0 (m,2H, H-5′ and H-5″), 2.1-2.0 (m, 9H, 3 CH₃CO₂), 1.78 (s, 1H, CH₃), 1.20(s, 3H, CH₃); MS (matrix GT): FAB>0 m/z 797 (2M+H)⁺, 399 (M+H)⁺, 339(M−CH₃CO₂)⁺, 273 (S)⁺, 127 (BH₂)⁺, 43 (CH₃CO)⁺ FAB<0 m/z 795 (2M−H)⁻,397 (M−H)⁻, 355 (M−CH₃CO)⁻, 125 (B)⁻, 59 (CH₃CO₂)⁻.

Example 16 Preparation of1-(5,2,3-Tri-O-acetyl-4-C-methyl-β-D-ribofuranosyl)-4-thio-thymine (16)

[0293] Lawesson's reagent (119 mg, 0.29 mmol) was added under argon to asolution of 15 (0.167 g, 4.19 mmol) in anhydrous 1,2-dichloroethane (11mL) and the reaction mixture was stirred overnight under reflux. Thesolvent was evaporated under reduced pressure and the residue waspurified by silica gel column chromatography [eluent: stepwise gradientof methanol (1-2%) in chloroform] to give pure 16 (0.165 g, 95%) as ayellow foam. ¹H-NMR (DMSO-d₆): δ12.81 (s, 1H, NH), 7.64 (s, 1H, H-6),5.84(d, 1H, H-1′, J_(1′-2′)=4.66 Hz), 5.5-5.4 (m, 2H, H-2′ and H-3′),4.11 (dd, 2H, H-5′ and H-5″, J=11.7 Hz, J=31.3 Hz), 2.0-1.8 (m, 12H, 3CH₃CO₂ and CH₃), 1.33 (s, 3H, CH₃); MS (matrix GT): FAB>0 m/z 829(2M+H)⁺, 415 (M+H)⁺, 273 (S)⁺, 143 (BH₂)⁺, 43 (CH₃CO)⁺ FAB<0 m/z 827(2M−H)⁻, 413 (M−H)⁻, 141 (B)³¹ , 59 (CH₃CO₂)⁻.

[0294] In a similar manner, the following nucleosides of Formula II areprepared, using the appropriate sugar and pyrimidine bases. (II)wherein: R¹ R² R³ X¹ Y H H H H H H H H H NH₂ H H H H NH-cyclopropyl H HH H NH-methyl H H H H NH-ethyl H H H H NH-acetyl H H H H OH H H H H OMeH H H H OEt H H H H O-cyclopropyl H H H H O-acetyl H H H H SH H H H HSMe H H H H SEt H H H H S-cyclopropyl monophosphate H H H NH₂monophosphate H H H NH-acetyl monophosphate H H H NH-cyclopropylmonophosphate H H H NH-methyl monophosphate H H H NH-ethyl monophosphateH H H OH monophosphate H H H O-acetyl monophosphate H H H OMemonophosphate H H H OEt monophosphate H H H O-cyclopropyl monophosphateH H H SH monophosphate H H H SMe monophosphate H H H SEt monophosphate HH H S-cyclopropyl diphosphate H H H NH₂ diphosphate H H H NH-acetyldiphosphate H H H NH-cyclopropyl diphosphate H H H NH-methyl diphosphateH H H NH-ethyl diphosphate H H H OH diphosphate H H H O-acetyldiphosphate H H H OMe diphosphate H H H OEt diphosphate H H HO-cyclopropyl diphosphate H H H SH diphosphate H H H SMe diphosphate H HH SEt diphosphate H H H S-cyclopropyl triphosphate H H H NH₂triphosphate H H H NH-acetyl triphosphate H H H NH-cyclopropyltriphosphate H H H NH-methyl triphosphate H H H NH-ethyl triphosphate HH H OH triphosphate H H H OMe triphosphate H H H OEt triphosphate H H HO-cyclopropyl triphosphate H H H O-acetyl triphosphate H H H SHtriphosphate H H H SMe triphosphate H H H SEt triphosphate H H HS-cyclopropyl monophosphate monophosphate monophosphate H NH₂monophosphate monophosphate monophosphate H NH-cyclopropyl monophosphatemonophosphate monophosphate H OH diphosphate diphosphate diphosphate HNH₂ diphosphate diphosphate diphosphate H NH-cyclopropyl diphosphatediphosphate diphosphate H OH triphosphate triphosphate triphosphate HNH₂ triphosphate triphosphate triphosphate H NH-cyclopropyl triphosphatetriphosphate triphosphate H OH H H H F NH₂ H H H F NH-cyclopropyl H H HF OH H H H Cl NH₂ H H H Cl NH-cyclopropyl H H H Cl OH H H H Br NH₂ H H HBr NH-cyclopropyl H H H Br OH H H H NH₂ NH₂ H H H NH₂ NH-cyclopropyl H HH NH₂ OH H H H SH NH₂ H H H SH NH-cyclopropyl H H H SH OH acetyl H H HNH₂ acetyl H H H NH-cyclopropyL acetyl H H H OH acetyl H H F NH₂ acetylH H F NH-cyclopropyl acetyl H H F OH H acetyl acetyl H NH₂ H acetylacetyl H NH-cyclopropyl H acetyl acetyl H OH acetyl acetyl acetyl H NH₂acetyl acetyl acetyl H NH-cyclopropyl acetyl acetyl acetyl H OHmonophosphate acetyl acetyl H NH₂ monophosphate acetyl acetyl HNH-cyclopropyl monophosphate acetyl acetyl H OH diphosphate acetylacetyl H NH₂ diphosphate acetyl acetyl H NH-cyclopropyl diphosphateacetyl acetyl H OH triphosphate acetyl acetyl H NH₂ triphosphate acetylacetyl H NH-cyclopropyl triphosphate acetyl acetyl H OH

Example 17 Preparation of1-(4-C-methyl-β-D-ribofuranosyl)-5-methyl-cytosine (17), HydrochlorideForm

[0295] Compound 16 (0.160 g, 0.386 mmol) was treated with methanolicammonia (previously saturated at −10° C.), (10 mL) at 100° C. in astainless-steel bomb for 3 hours, then cooled to room temperature. Thesolvent was evaporated under reduced pressure and the residue waspartitioned between methylene chloride (30 mL) and water (30 mL). Theaqueous layer was washed with methylene chloride (2×30 mL), concentratedunder reduced pressure. The crude material was purified by silica gelcolumn chromatography [eluent: 20% methanol in methylene chloride] toafford 1-(4-C-methyl-β-D-ribofuranosyl)-5-methyl-cytosine (60 mg, 57%).This compound was dissolved in EtOH 100 (1.5 mL), treated with a 2Nhydrochloric acid solution (0.3 mL), and the mixture was stirred beforebeing concentrated under reduced pressure. The procedure was repeatedtwice and 17 was precipitated from absolute ethanol. Mp: 194-200 (dec.);UV (H₂O): λ_(max)=275.6 nm (ε=7300), λ_(min)=255 nm (ε=4700); HPLC 100%,¹H-NMR (DMSO-d₆): δ9.34 and 9.10 (2s, 2H, NH₂), 8.21 (s, 1H, H-6), 5.80(d, 1H, H-1′, J_(1′-2′)=6.0 Hz), 5.3-4.3 (m, 3H, OH-2′, OH-3′ andOH-5′), 4.21 (t, 1H, H-2′, J=5.7 Hz), 3.98 (d, 1H, H-3′, J=5.3 Hz),3.5-3.3 (m, 2H, H-5′ and H-5″), 1.97 (s, 3H, CH₃), 1.12 (s, 3H, CH₃).

Example 18 Preparation ofO-6-Diphenylcarbamoyl-N²-isobutyryl-9-(2,3-di-O-acetyl-5-O-benzoyl-4-C-methyl-β-D-ribofuranosyl)guanine(18)

[0296] To a suspension of O-6-diphenylcarbamoyl-N²-isobutyrylguanine(1.80 g, 4.33 mmol) in anhydrous toluene (20 mL) was addedN,O-bis(trimethylsilyl)acetamide (1.92 mL, 7.9 mmol). The reactionmixture was allowed to warm under reflux for 1 hour. Compound 7 (1.55 g,3.93 mmol) was dissolved in toluene (10 mL) andtrimethylsilyltrifluoromethanesulfonate (TMSTF) (915 mL, 4.72 mmol) wasadded. The mixture was heated under reflux for 30 minutes. The solutionwas then cooled to room temperature and neutralized with a 5% aqueoussodium hydrogen carbonate solution. The reaction mixture was dilutedwith ethyl acetate (200 mL). The organic phase was washed with a 5%aqueous sodium hydrogen carbonate solution (150 mL) and with water(2×150 mL). The organic layer was dried over Na₂SO₄ and evaporated todryness. The residue was purified by silica gel column chromatography[eluent: stepwise gradient of diethyl ether (70-90%) in petroleum ether]to afford pure 18 (1.62 g, 55%) as a foam.

Example 19 Preparation of 9-(4-C-methyl-β-D-ribofuranosyl) guanine (19)

[0297] The title compound can be prepared according to a publishedprocedure from 18 (Waga, T.; Nishizaki, T.; Miyakawa, I.; Orhui, H.;Meguro, H. “Synthesis of 4′-C-methylnucleosides” Biosci. Biotechnol.Biochem. 1993, 57, 1433-1438).

[0298] A solution of 18 (1.50 g, mmol) in methanolic ammonia (previouslysaturated at −10° C.) (20 mL) was stirred at room temperature overnight.The solvent was evaporated under reduced pressure and the residue waspartitioned between methylene chloride (60 mL) and water (60 mL). Theaqueous layer was washed with methylene chloride (2×60 mL), concentratedunder reduced pressure. The residue was purified by an RP18 columnchromatography [eluent water/acetonitrile 95/5] to afford pure 19 (380mg, 60%). Recrystallization from water gave 19 as a crystalline solid.Mp>300 (dec.), UV (H₂O): λ_(max)=252 nm (ε=14500), ¹H-NMR (DMSO-d₆):δ10.64 (s, 1H, NH), 7.95 (s, 1H, H-8), 6.45 (s1, 2H, NH₂), 5.68 (d, 1H,H-1′, J_(1′-2′)=7.45 Hz), 5.31 (d, 1H, OH, OH-2′,J_(OH-2′)=6.8 Hz), 5.17(t, 1H, OH, OH-5′, J=5.5 Hz), 5.07 (d, 1H, OH-3′, J_(OH-3′)=4.5 Hz),4.65 (dd, 1H, H-2′, J=7.1 Hz, J=12.2 Hz), 4.00 (t, 1H, H-3′,J_(3′-2′)=J_(3′-OH′)=4.8 Hz), 3.41 (m, 2H, H-5′ and H-5″), 1.12 (s, 3H,CH₃); MS (matrix GT): FAB>0 m/z 595 (2M+H)⁺, 390 (M+G+H)⁺, 298 (M+H)⁺,152 (B+2H)⁺, FAB<0 m/z 593 (2M−H)⁻, 296 (M−H)⁻, 150 (B)⁻.

Example 209-(2,3-di-O-acetyl-5-O-benzoyl-4-C-methyl-β-D-ribofuranosyl)adenine (20)

[0299] A solution of 7 (1.10 g, 2.79 mmol) in anhydrous acetonitrile (50ml) was treated with adenine (452.4 mg, 3.35 mmol) and stannic chloride(SnCl₄, 660 μL, 5.58 mmol) and stirred at room temperature overnight.The solution was concentrated under reduced pressure, diluted withchloroform (100 mL) and treated with a cold saturated aqueous solutionof NaHCO₃ (100 ml). The mixture was filtered on celite, and theprecipitate was washed with hot chloroform. The filtrates were combined,washed with water (100 ml) and brine (100 ml), dried (Na₂SO₄), andevaporated under reduced pressure. The residue was purified by silicagel column chromatography [eluent: stepwise gradient of methanol (3-5%)in dichloromethane] to afford pure 20 (977 mg, 77%) as a white foam.¹H-NMR (DMSO-d₆): δ8.31-7.49 (m, 7H, C₆H₅CO, H-2 and H-8), 7.37 (ls, 2H,NH₂) 6.27 (m, 2H, H-1′ and H-3′), 5.90 (m, 1H, H-2′), 4.60 (d, 1H, H-5′,J=11.7 Hz), 4.35 (d, 1H, H-5′), 2.17 (s, 3H, CH₃CO₂), 2.06 (s, 3H,CH₃CO₂), 1.42 (s, 3H, CH₃).

Example 21 Preparation of 9-(4-C-methyl-β-D-ribofuranosyl) adenine (21)

[0300] The title compound can be prepared according to a publishedprocedure from 20 (Waga, T.; Nishizaki, T.; Miyakawa, I.; Orhui, H.;Meguro, H. “Synthesis of 4′-C-methylnucleosides” Biosci. Biotechnol.Biochem. 1993, 57, 1433-1438).

[0301] A solution of 20 (970 mg, 2.08 mmol) in methanolic ammonia(previously saturated at −10° C.) (50 mL) was stirred at roomtemperature overnight. The solvent was evaporated under reduced pressureand the residue was partitioned between methylene chloride (100 ml) andwater (100 ml). The aqueous layer was washed with methylene chloride(2×100 mL), and concentrated under reduced pressure. The residue waspurified by silica gel column chromatography [eluent: stepwise gradientof methanol (10-30%) in ethyl acetate] to afford pure 21 (554 mg, 95%).Crystallization from methanol/ethyl acetate gave 21 as a white solid.Mp: 96-97 (dec.); ¹H-NMR (DMSO-d₆): δ8.33 (s, 1H, H-2), 8.13 (s, 1H,H-8), 7.36 (brs, 2H, NH2), 5.84 (d, 1H, H-1′, J_(1′-2′)=7.4 Hz), 5.69(dd, 1H, OH-5′, J=4.2 Hz and J=7.8 Hz), 5.33 (d, 1H, OH-2′, J=6.6 Hz),5.13 (d, 1H, OH-3′, J=4.4 Hz), 4.86 (m, 1H, H-2′), 4.04 (t, 1H, H-3′),3.58-3.32 (m, 2H, H-5′ and H-5″), 1.15 (s, 3H, CH₃); MS (matrix GT):FAB>0 m/z 563 (2M+H)⁺, 374 (M+G+H)⁺, 282 (M+H)⁺, 136 (B+2H)⁺, FAB<0 m/z561 (2M−H)⁻, 280 (M−H)⁻, 134 (B)⁻.

[0302] In a similar manner, the following nucleosides of Formula I areprepared, using the appropriate sugar and purine bases. (I)

wherein: R R² R³ X¹ X² Y H H H H H H H H H H H NH₂ H H H H HNH-cyclopropyl H H H H H NH-methyl H H H H H NH-ethyl H H H H HNH-acetyl H H H H H OH H H H H H OMe H H H H H OEt H H H H HO-cyclopropyl H H H H H O-acetyl H H H H H SH H H H H H SMe H H H H HSEt H H H H H S-cyclopropyl H H H H H F H H H H H Cl H H H H H Br H H HH H I monophosphate H H H H NH₂ monophosphate H H H H NH-acetylmonophosphate H H H H NH-cyclopropyl monophosphate H H H H NH-methylmonophosphate H H H H NH-ethyl monophosphate H H H H OH monophosphate HH H H O-acetyl monophosphate H H H H OMe monophosphate H H H H OEtmonophosphate H H H H O-cyclopropyl monophosphate H H H H SHmonophosphate H H H H SMe monophosphate H H H H SEt monophosphate H H HH S-cyclopropyl monophosphate H H H H F monophosphate H H H H Clmonophosphate H H H H Br monophosphate H H H H I diphosphate H H H H NH₂diphosphate H H H H NH-acetyl diphosphate H H H H NH-cyclopropyldiphosphate H H H H NH-methyl diphosphate H H H H NH-ethyl diphosphate HH H H OH diphosphate H H H H O-acetyl diphosphate H H H H OMediphosphate H H H H OEt diphosphate H H H H O-cyclopropyl diphosphate HH H H SH diphosphate H H H H SMe diphosphate H H H H SEt diphosphate H HH H S-cyclopropyl diphosphate H H H H F diphosphate H H H H Cldiphosphate H H H H Br diphosphate H H H H I triphosphate H H H H NH₂triphosphate H H H H NH-acetyl triphosphate H H H H NH-cyclopropyltriphosphate H H H H NH-methyl triphosphate H H H H NH-ethyltriphosphate H H H H OH tnphosphate H H H H OMe triphosphate H H H H OEttriphosphate H H H H O-cyclopropyl triphosphate H H H H O-acetyltriphosphate H H H H SH triphosphate H H H H SMe triphosphate H H H HSEt triphosphate H H H H S-cyclopropyl triphosphate H H H H Ftriphosphate H H H H Cl triphosphate H H H H Br triphosphate H H H H Imonophosphate monophosphate monophosphate H H NH₂ monophosphatemonophosphate monophosphate H H NH-cyclopropyl monophosphatemonophosphate monophosphate H H OH monophosphate monophosphatemonophosphate H H F monophosphate monophosphate monophosphate H H Cldiphosphate diphosphate diphosphate H H NH₂ diphosphate diphosphatediphosphate H H NH-cyclopropyl diphosphate diphosphate diphosphate H HOH diphosphate diphosphate diphosphate H H F diphosphate diphosphatediphosphate H H CI triphosphate triphosphate triphosphate H H NH₂triphosphate triphosphate triphosphate H H NH-cyclopropyl triphosphatetriphosphate triphosphate H H OH triphosphate triphosphate triphosphateH H F triphosphate triphosphate triphosphate H H Cl H H H F H NH₂ H H HF H NH-cyclopropyl H H H F H OH H H H F H F H H H F H Cl H H H Cl H NH₂H H H Cl H NH-cyclopropyl H H H Cl H OH H H H Cl H F H H H Cl H Cl H H HBr H NH₂ H H H Br H NH-cyclopropyl H H H Br H OH H H H Br H F H H H Br HCl H H H NH₂ H NH₂ H H H NH₂ H NH-cyclopropyl H H H NH₂ H OH H H H NH₂ HF H H H NH₂ H Cl H H H SH H NH₂ H H H SH H NH-cyclopropyl H H H SH H OHH H H SH H F H H H SH H Cl acetyl H H H H NH₂ acetyl H H H HNH-cyclopropyl acetyl H H H H OH acetyl H H H H F acetyl H H H H Clacetyl H H F H NH₂ acetyl H H F H NH-cyclopropyl acetyl H H F H OHacetyl H H F H F acetyl H H F H Cl H acetyl acetyl H H NH₂ H acetylacetyl H H NH-cyclopropyl H acetyl acetyl H H OH H acetyl acetyl H H F Hacetyl acetyl H H Cl acetyl acetyl acetyl H H NH₂ acetyl acetyl acetyl HH NH-cyclopropyl acetyl acetyl acetyl H H OH acetyl acetyl acetyl H H Facetyl acetyl acetyl H H Cl monophosphate acetyl acetyl H H NH₂monophosphate acetyl acetyl H H NH-cyclopropyl monophosphate acetylacetyl H H OH monophosphate acetyl acetyl H H F monophosphate acetylacetyl H H Cl diphosphate acetyl acetyl H H NH₂ diphosphate acetylacetyl H H NH-cyclopropyl diphosphate acetyl acetyl H H OH diphosphateacetyl acetyl H H F diphosphate acetyl acetyl H H Cl triphosphate acetylacetyl H H NH₂ triphosphate acetyl acetyl H H NH-cyclopropyltriphosphate acetyl acetyl H H OH triphosphate acetyl acetyl H H Ftriphosphate acetyl acetyl H H Cl H H H H NH₂ H H H H H NH₂ NH₂ H H H HNH₂ NH-cyclopropyl H H H H NH₂ NH-methyl H H H H NH₂ NH-ethyl H H H HNH₂ NH-acetyl H H H H NH₂ OH H H H H NH₂ OMe H H H H NH₂ OEt H H H H NH₂O-cyclopropyl H H H H NH₂ O-acetyl H H H H NH₂ SH H H H H NH₂ SMe H H HH NH₂ SEt H H H H NH₂ S-cyclopropyl H H H H NH₂ F H H H H NH₂ Cl H H H HNH₂ Br H H H H NH₂ I monophosphate H H H NH₂ NH₂ monophosphate H H H NH₂NH-acetyl monophosphate H H H NH₂ NH-cyclopropyl monophosphate H H H NH₂NH-methyl monophosphate H H H NH₂ NH-ethyl monophosphate H H H NH₂ OHmonophosphate H H H NH₂ O-acetyl monophosphate H H H NH₂ OMemonophosphate H H H NH₂ OEt monophosphate H H H NH₂ O-cyclopropylmonophosphate H H H NH₂ SH monophosphate H H H NH₂ SMe monophosphate H HH NH₂ SEt monophosphate H H H NH₂ S-cyclopropyl monophosphate H H H NH₂F monophosphate H H H NH₂ Cl monophosphate H H H NH₂ Br monophosphate HH H NH₂ I diphosphate H H H NH₂ NH₂ diphosphate H H H NH₂ NH-acetyldiphosphate H H H NH₂ NH-cyclopropyl diphosphate H H H NH₂ NH-methyldiphosphate H H H NH₂ NH-ethyl diphosphate H H H NH₂ OH diphosphate H HH NH₂ O-acetyl diphosphate H H H NH₂ OMe diphosphate H H H NH₂ OEtdiphosphate H H H NH₂ O-cyclopropyl diphosphate H H H NH₂ SH diphosphateH H H NH₂ SMe diphosphate H H H NH₂ SEt diphosphate H H H NH₂S-cyclopropyl diphosphate H H H NH₂ F diphosphate H H H NH₂ Cldiphosphate H H H NH₂ Br diphosphate H H H NH₂ I triphosphate H H H NH₂NH₂ triphosphate H H H NH₂ NH-acetyl triphosphate H H H NH₂NH-cyclopropyl tnphosphate H H H NH₂ NH-methyl triphosphate H H H NH₂NH-ethyl triphosphate H H H NH₂ OH triphosphate H H H NH₂ OMetriphosphate H H H NH₂ OEt triphosphate H H H NH₂ O-cyclopropyltriphosphate H H H NH₂ O-acetyl triphosphate H H H NH₂ SH triphosphate HH H NH₂ SMe triphosphate H H H NH₂ SEt triphosphate H H H NH₂S-cyclopropyl triphosphate H H H NH₂ F triphosphate H H H NH₂ Cltriphosphate H H H NH₂ Br triphosphate H H H NH₂ I monophosphatemonophosphate monophosphate H NH₂ NH₂ monophosphate monophosphatemonophosphate H NH₂ NH-cyclopropyl monophosphate monophosphatemonophosphate H NH₂ OH monophosphate monophosphate monophosphate H NH₂ Fmonophosphate monophosphate monophosphate H NH₂ Cl diphosphatediphosphate diphosphate H NH₂ NH₂ diphosphate diphosphate diphosphate HNH₂ NH-cyclopropyl diphosphate diphosphate diphosphate H NH₂ OHdiphosphate diphosphate diphosphate H NH₂ F diphosphate diphosphatediphosphate H NH₂ Cl triphosphate triphosphate triphosphate H NH₂ NH₂triphosphate triphosphate triphosphate H NH₂ NH-cyclopropyl triphosphatetriphosphate triphosphate H NH₂ OH triphosphate triphosphatetriphosphate H NH₂ F triphosphate triphosphate triphosphate H NH₂ Cl H HH F NH₂ NH₂ H H H F NH₂ NH-cyclopropyl H H H F NH₂ OH H H H F NH₂ F H HH F NH₂ Cl H H H Cl NH₂ NH₂ H H H Cl NH₂ NH-cyclopropyl H H H Cl NH₂ OHH H H Cl NH₂ F H H H CI NH₂ Cl H H H Br NH₂ NH₂ H H H Br NH₂NH-cyclopropyl H H H Br NH₂ OH H H H Br NH₂ F H H H Br NH₂ Cl H H H NH₂NH₂ NH₂ H H H NH₂ NH₂ NH-cyclopropyl H H H NH₂ NH₂ OH H H H NH₂ NH₂ F HH H NH₂ NH₂ Cl H H H SH NH₂ NH₂ H H H SH NH₂ NH-cyclopropyl H H H SH NH₂OH H H H SH NH₂ F H H H SH NH₂ Cl acetyl H H H NH₂ NH₂ acetyl H H H NH₂NH-cyclopropyl acetyl H H H NH₂ OH acetyl H H H NH₂ F acetyl H H H NH₂Cl acetyl H H F NH₂ NH₂ acetyl H H F NH₂ NH-cyclopropyl acetyl H H F NH₂OH acetyl H H F NH₂ F acetyl H H F NH₂ Cl H acetyl acetyl H NH₂ NH₂ Hacetyl acetyl H NH₂ NH-cyclopropyl H acetyl acetyl H NH₂ OH H acetylacetyl H NH₂ F H acetyl acetyl H NH₂ Cl acetyl acetyl acetyl H NH₂ NH₂acetyl acetyl acetyl H NH₂ NH-cyclopropyl acetyl acetyl acetyl H NH₂ OHacetyl acetyl acetyl H NH₂ F acetyl acetyl acetyl H NH₂ Cl monophosphateacetyl acetyl H NH₂ NH₂ monophosphate acetyl acetyl H NH₂ NH-cyclopropylmonophosphate acetyl acetyl H NH₂ OH monophosphate acetyl acetyl H NH₂ Fmonophosphate acetyl acetyl H NH₂ Cl diphosphate acetyl acetyl H NH₂ NH₂diphosphate acetyl acetyl H NH₂ NH-cyclopropyl diphosphate acetyl acetylH NH₂ OH diphosphate acetyl acetyl H NH₂ F diphosphate acetyl acetyl HNH₂ Cl triphosphate acetyl acetyl H NH₂ NH₂ triphosphate acetyl acetyl HNH₂ NH-cyclopropyl triphosphate acetyl acetyl H NH₂ OH triphosphateacetyl acetyl H NH₂ F triphosphate acetyl acetyl H NH₂ Cl H H H H Cl H HH H H Cl H H H H H Cl NH₂ H H H H Cl NH-cyclopropyl H H H H Cl NH-methylH H H H Cl NH-ethyl H H H H Cl NH-acetyl H H H H Cl OH H H H H Cl OMe HH H H Cl OEt H H H H Cl O-cyclopropyl H H H H Cl O-acetyl H H H H Cl SHH H H H Cl SMe H H H H Cl SEt H H H H Cl S-cyclopropyl monophosphate H HH Cl NH₂ monophosphate H H H Cl NH-acetyl monophosphate H H H ClNH-cyclopropyl monophosphate H H H Cl NH-methyl monophosphate H H H ClNH-ethyl monophosphate H H H Cl OH monophosphate H H H Cl O-acetylmonophosphate H H H Cl OMe monophosphate H H H Cl OEt monophosphate H HH Cl O-cyclopropyl monophosphate H H H Cl SH monophosphate H H H Cl SMemonophosphate H H H Cl SEt monophosphate H H H Cl S-cyclopropyldiphosphate H H H Cl NH₂ diphosphate H H H Cl NH-acetyl diphosphate H HH Cl NH-cyclopropyl diphosphate H H H Cl NH-methyl diphosphate H H H ClNH-ethyl diphosphate H H H Cl OH diphosphate H H H Cl O-acetyldiphosphate H H H Cl OMe diphosphate H H H Cl OEt diphosphate H H H ClO-cyclopropyl diphosphate H H H Cl SH diphosphate H H H Cl SMediphosphate H H H Cl SEt diphosphate H H H Cl S-cyclopropyl triphosphateH H H Cl NH₂ triphosphate H H H Cl NH-acetyl triphosphate H H H ClNH-cyclopropyl triphosphate H H H Cl NH-methyl triphosphate H H H ClNH-ethyl triphosphate H H H Cl OH triphosphate H H H Cl OMe triphosphateH H H Cl OEt triphosphate H H H Cl O-cyclopropyl triphosphate H H H ClO-acetyl triphosphate H H H Cl SH triphosphate H H H Cl SMe triphosphateH H H Cl SEt triphosphate H H H Cl S-cyclopropyl monophosphatemonophosphate monophosphate H Cl NH₂ monophosphate monophosphatemonophosphate H Cl NH-cyclopropyl monophosphate monophosphatemonophosphate H Cl OH diphosphate diphosphate diphosphate H Cl NH₂diphosphate diphosphate diphosphate H Cl NH-cyclopropyl diphosphatediphosphate diphosphate H Cl OH triphosphate triphosphate triphosphate HCl NH₂ triphosphate triphosphate triphosphate H Cl NH-cyclopropyltriphosphate triphosphate triphosphate H Cl OH H H H F Cl NH₂ H H H F ClNH-cyclopropyl H H H F Cl OH H H H Cl Cl NH₂ H H H Cl Cl NH-cyclopropylH H H Cl Cl OH H H H Br Cl NH₂ H H H Br Cl NH-cyclopropyl H H H Br Cl OHH H H NH₂ Cl NH₂ H H H NH₂ Cl NH-cyclopropyl H H H NH₂ Cl OH H H H SH ClNH₂ H H H SH Cl NH-cyclopropyl H H H SH Cl OH acetyl H H H Cl NH₂ acetylH H H Cl NH-cyclopropyl acetyl H H H Cl OH acetyl H H F Cl NH₂ acetyl HH F Cl NH-cyclopropyl acetyl H H F Cl OH H acetyl acetyl H Cl NH₂ Hacetyl acetyl H Cl NH-cyclopropyl H acetyl acetyl H Cl OH acetyl acetylacetyl H Cl NH₂ acetyl acetyl acetyl H Cl NH-cyclopropyl acetyl acetylacetyl H Cl OH monophosphate acetyl acetyl H Cl NH₂ monophosphate acetylacetyl H Cl NH-cyclopropyl monophosphate acetyl acetyl H Cl OHdiphosphate acetyl acetyl H Cl NH₂ diphosphate acetyl acetyl H ClNH-cyclopropyl diphosphate acetyl acetyl H Cl OH triphosphate acetylacetyl H Cl NH₂ triphosphate acetyl acetyl H Cl NH-cyclopropyltriphosphate acetyl acetyl H Cl OH H H H H Cl NH₂ H H H H ClNH-cyclopropyl H H H H Cl OH H H H H Br NH₂ H H H H Br NH-cyclopropyl HH H H Br OH

[0303] Alternatively, the following nucleosides of Formula III areprepared, using the appropriate sugar and pyrimidine or purine bases.(III)

wherein: R¹ R² R³ R⁶ X Base H H H CH₃ O 2,4-O- Diacetyluracil H H H CH₃O Hypoxanthine H H H CH₃ O 2,4-O- Diacetylthymine H H H CH₃ O Thymine HH H CH₃ O Cytosine H H H CH₃ O 4-(N-mono- acetyl)cytosine H H H CH₃ O4-(N,N- diacetyl)cytosine H H H CH₃ O Uracil H H H CH₃ O 5-FluorouracilH H H CH₃ S 2,4-O- Diacetyluraci H H H CH₃ S Hypoxanthine H H H CH₃ S2,4-O- Diacetylthymine H H H CH₃ S Thymine H H H CH₃ S Cytosine H H HCH₃ S 4-(N-mono- acetyl)cytosine H H H CH₃ S 4-(N,N- diacetyl)cytosine HH H CH₃ S Uracil H H H CH₃ S 5-Fluorouracil monophosphate H H CH₃ O2,4-O- Diacetyluracil monophosphate H H CH₃ O Hypoxanthine monophosphateH H CH₃ O 2,4-O- Diacetylthym monophosphate H H CH₃ O Thyminemonophosphate H H CH₃ O Cytosine monophosphate H H CH₃ O 4-(N-mono-acetyl)cytosine monophosphate H H CH₃ O 4-(N,N- diacetyl)cytosinemonophosphate H H CH₃ O Uracil monophosphate H H CH₃ O 5-Fluorouracilmonophosphate H H CH₃ S 2,4-O- Diacetyluracil monophosphate H H CH₃ SHypoxanthine monophosphate H H CH₃ S 2,4-O- Diacetylthym monophosphate HH CH₃ S Thymine monophosphate H H CH₃ S Cytosine monophosphate H H CH₃ S4-(N-mono- acetyl)cytosine monophosphate H H CH₃ S 4-(N,N-diacetyl)cytosine monophosphate H H CH₃ S Uracil monophosphate H H CH₃ S5-Fluorouracil diphosphate H H CH₃ O 2,4-O- Diacetyluracil diphosphate HH CH₃ O Hypoxanthine diphosphate H H CH₃ O 2,4-O- Diacetylthyminediphosphate H H CH₃ O Thymine diphosphate H H CH₃ O Cytosine diphosphateH H CH₃ O 4-(N-mono- acetyl)cytosine diphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine diphosphate H H CH₃ O Uracil diphosphate H H CH₃ O5-Fluorouracil diphosphate H H CH₃ S 2,4-O- Diacetyluracil diphosphate HH CH₃ S Hypoxanthine diphosphate H H CH₃ S 2,4-O- Diacetylthymdiphosphate H H CH₃ S Thymine diphosphate H H CH₃ S Cytosinetriphosphate H H CH₃ O 2,4-O- Diacetyluracil triphosphate H H CH₃ OHypoxanthine triphosphate H H CH₃ O 2,4-O- Diacetylthymine triphosphateH H CH₃ O Thymine triphosphate H H CH₃ O Cytosine triphosphate H H CH₃ O4-(N-mono- acetyl)cytosine triphosphate H H CH₃ O 4-(N,N-diacetyl)cytosine triphosphate H H CH₃ O Uracil triphosphate H H CH₃ O5-Fluorouracil triphosphate H H CH₃ S 2,4-O- Diacetyluracil triphosphateH H CH₃ S Hypoxanthine triphosphate H H CH₃ S 2,4-O- Diacetylthyminetriphosphate H H CH₃ S Thymine triphosphate H H CH₃ S Cytosinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetyluracilmonophosphate monophosphate monophosphate CF₃ O Hypoxanthinemonophosphate monophosphate monophosphate CF₃ O 2,4-O- Diacetylthyminemonophosphate monophosphate monophosphate CF₃ O Thymine monophosphatemonophosphate monophosphate CF₃ O Cytosine monophosphate monophosphatemonophosphate CF₃ O 4-(N-mono- acetyl)cytosine monophosphatemonophosphate monophosphate CF₃ O 4-(N,N- diacetyl)cytosinemonophosphate monophosphate monophosphate CF₃ O Uracil monophosphatemonophosphate monophosphate CF₃ O 5-Fluorouracil monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetyluracil monophosphatemonophosphate monophosphate CF₃ S Hypoxanthine monophosphatemonophosphate monophosphate CF₃ S 2,4-O- Diacetylthymine monophosphatemonophosphate monophosphate CF₃ S Thymine monophosphate monophosphatemonophosphate CF₃ S Cytosine monophosphate monophosphate monophosphateCF₃ S 4-(N-mono- acetyl)cytosine monophosphate monophosphatemonophosphate CF₃ S 4-(N,N- diacetyl)cytosine monophosphatemonophosphate monophosphate CF₃ S Uracil monophosphate monophosphatemonophosphate CF₃ S 5-Fluorouracil acetyl acetyl acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl acetyl acetyl CF₃ S 4-(N,N- diacetyl)cytosineacetyl acetyl acetyl 2-bromo- O 4-(N,N- vinyl diacetyl)cytosine acetylacetyl acetyl 2-bromo- S 4-(N,N- vinyl diacetyl)cytosine H H H CH₃ O2-(N,N-diacetyl)- guanine H H H CH₃ O 6-O-acetyl guanine H H H CH₃ O8-fluoroguanine H H H CH₃ O guanine H H H CH₃ O 6-(N,N-diacetyl)-adenine H H H CH₃ O 2-fluoroadenine H H H CH₃ O 8-fluoroadenine H H HCH₃ O 2,8-difluoro- adenine H H H CH₃ O adenine H H H CH₃ S2-(N,N-diacetyl)- guanine H H H CH₃ S 6-O-acetyl guanine H H H CH₃ S8-fluoroguanine H H H CH₃ S guanine H H H CH₃ S 6-(N,N-diacetyl)-adenine H H H CH₃ S 2-fluoroadenine H H H CH₃ S 8-fluoroadenine H H HCH₃ S 2,8-difluoro- adenine H H H CH₃ S adenine monophosphate H H CH₃ O2-(N,N-diacetyl)- guanine monophosphate H H CH₃ O 6-O-acetyl guaninemonophosphate H H CH₃ O 8-fluoroguanine monophosphate H H CH₃ O guaninemonophosphate H H CH₃ O 6-(N,N-diacetyl)- adenine monophosphate H H CH₃O 2-fluoroadenine monophosphate H H CH₃ O 8-fluoroadenine monophosphateH H CH₃ O 2,8-difluoro- adenine monophosphate H H CH₃ O adeninemonophosphate H H CH₃ S 2-(N,N-diacetyl)- guanine monophosphate H H CH₃S 6-O-acetyl guanine monophosphate H H CH₃ S 8-fluoroguaninemonophosphate H H CH₃ S guanine monophosphate H H CH₃ S6-(N,N-diacetyl)- adenine monophosphate H H CH₃ S 2-fluoroadeninemonophosphate H H CH₃ S 8-fluoroadenine monophosphate H H CH₃ S2,8-difluoro- adenine monophosphate H H CH₃ S adenine diphosphate H HCH₃ O 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ O 6-O-acetyl guaninediphosphate H H CH₃ O 8-fluoroguanine diphosphate H H CH₃ O guaninediphosphate H H CH₃ O 6-(N,N-diacetyl)- adenine diphosphate H H CH₃ O2-fluoroadenine diphosphate H H CH₃ O 8-fluoroadenine diphosphate H HCH₃ O 2,8-difluoro- adenine diphosphate H H CH₃ O adenine diphosphate HH CH₃ S 2-(N,N-diacetyl)- guanine diphosphate H H CH₃ S 6-O-acetylguanine diphosphate H H CH₃ S 8-fluoroguanine diphosphate H H CH₃ Sguanine diphosphate H H CH₃ S 6-(N,N-diacetyl)- adenine diphosphate H HCH₃ S 2-fluoroadenine diphosphate H H CH₃ S 8-fluoroadenine diphosphateH H CH₃ S 2,8-difluoro- adenine diphosphate H H CH₃ S adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ O6-O-acetyl guanine triphosphate H H CH₃ O 8-fluoroguanine triphosphate HH CH₃ O guanine triphosphate H H CH₃ O 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ O 2-fluoroadenine triphosphate H H CH₃ O8-fluoroadenine triphosphate H H CH₃ O 2,8-difluoro- adeninetriphosphate H H CH₃ O 2-(N,N-diacetyl)- guanine triphosphate H H CH₃ S6-O-acetyl guanine triphosphate H H CH₃ S 8-fluoroguanine triphosphate HH CH₃ S guanine triphosphate H H CH₃ S 6-(N,N-diacetyl)- adeninetriphosphate H H CH₃ S 2-fluoroadenine triphosphate H H CH₃ S8-fluoroadenine triphosphate H H CH₃ S 2,8-difluoro- adeninetriphosphate H H CH₃ S adenine monophosphate monophosphate monophosphateCF₃ O 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ O 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ O guanine monophosphate monophosphate monophosphateCF₃ O 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ O 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ O 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ O adenine monophosphate monophosphate monophosphateCF₃ S 2-(N,N-diacetyl)- guanine monophosphate monophosphatemonophosphate CF₃ S 6-O-acetyl guanine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroguanine monophosphate monophosphatemonophosphate CF₃ S guanine monophosphate monophosphate monophosphateCF₃ S 6-(N,N-diacetyl)- adenine monophosphate monophosphatemonophosphate CF₃ S 2-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 8-fluoroadenine monophosphate monophosphatemonophosphate CF₃ S 2,8-difluoro- adenine monophosphate monophosphatemonophosphate CF₃ S adenine acetyl acetyl acetyl CF₃ O guanine acetylacetyl acetyl CF₃ S guanine acetyl acetyl acetyl 2-bromo- O guaninevinyl acetyl acetyl acetyl 2-bromo- S guanine vinyl

[0304] Alternatively, the following nucleosides of Formula IV areprepared, using the appropriate sugar and pyrimidine or purine bases.(IV)

wherein R¹ R² R⁶ X Base H H CH₃ O 2,4-O-Diacetyluracil H H CH₃ OHypoxanthine H H CH₃ O 2,4-O-Diacetylthymine H H CH₃ O Thymine H H CH₃ OCytosine H H CH₃ O 4-(N-mono-acetyl)cytosine H H CH₃ O4-(N,N-diacetyl)cytosine H H CH₃ O Uracil H H CH₃ O 5-Fluorouracil H HCH₃ S 2,4-O-Diacetyluracil H H CH₃ S Hypoxanthine H H CH₃ S2,4-O-Diacetylthymine H H CH₃ S Thymine H H CH₃ S Cytosine H H CH₃ S4-(N-mono-acetyl)cytosine H H CH₃ S 4-(N,N-diacetyl)cytosine H H CH₃ SUracil H H CH₃ S 5-Fluorouracil mono- H CH₃ O 2,4-O-Diacetyluracilphosphate mono- H CH₃ O Hypoxanthine phosphate mono- H CH₃ O2,4-O-Diacetylthymine phosphate mono- H CH₃ O Thymine phosphate mono- HCH₃ O Cytosine phosphate mono- H CH₃ O 4-(N-mono-acetyl)cytosinephosphate mono- H CH₃ O 4-(N,N-diacetyl)cytosine phosphate mono- H CH₃ OUracil phosphate mono- H CH₃ O 5-Fluorouracil phosphate mono- H CH₃ S2,4-O-Diacetyluracil phosphate mono- H CH₃ S Hypoxanthine phosphatemono- H CH₃ S 2,4-O-Diacetylthymine phosphate mono- H CH₃ S Thyminephosphate mono- H CH₃ S Cytosine phosphate mono- H CH₃ S4-(N-mono-acetyl)cytosine phosphate mono- H CH₃ S4-(N,N-diacetyl)cytosine phosphate mono- H CH₃ S Uracil phosphate mono-H CH₃ S 5-Fluorouracil phosphate diphos- H CH₃ O 2,4-O-Diacetyluracilphate diphos- H CH₃ O Hypoxanthine phate diphos- H CH₃ O2,4-O-Diacetylthymine phate diphos- H CH₃ O Thymine phate diphos- H CH₃O Cytosine phate diphos- H CH₃ O 4-(N-mono-acetyl)cytosine phate diphos-H CH₃ O 4-(N,N-diacetyl)cytosine phate diphos- H CH₃ O Uracil phatediphos- H CH₃ O 5-Fluorouracil phate diphos- H CH₃ S2,4-O-Diacetyluracil phate diphos- H CH₃ S Hypoxanthine phate diphos- HCH₃ S 2,4-O-Diacetylthymine phate diphos- H CH₃ S Thymine phate diphos-H CH₃ S Cytosine phate diphos- H CH₃ S 4-(N-mono-acetyl)cytosine phatediphos- H CH₃ S 4-(N,N-diacetyl)cytosine phate diphos- H CH₃ S Uracilphate diphos- H CH₃ S 5-Fluorouracil phate triphos- H CH₃ O2,4-O-Diacelyluracil phate triphos- H CH₃ O Hypoxanthine phate triphos-H CH₃ O 2,4-O-diacethylthymine phate triphos- H CH₃ O Thymine phatetriphos- H CH₃ O Cytosine phate triphos- H CH₃ O4-(N-mono-acetyl)cytosine phate triphos- H CH₃ O4-(N,N-diacetyl)cytosine phate triphos- H CH₃ O Uracil phate triphos- HCH₃ O 5-Fluorouracil phate triphos- H CH₃ S 2,4-O-Diacetyluracil phatetriphos- H CH₃ S Hypoxanthine phate triphos- H CH₃ S2,4-O-Diacetylthymine phate triphos- H CH₃ S Thymine phate triphos- HCH₃ S Cytosine phate triphos- H CH₃ S 4-(N-mono-acetyl)cytosine phatetriphos- H CH₃ S 4-(N,N-diacetyl)cytosine phate triphos- H CH₃ S Uracilphate triphos- H CH₃ S 5-Fluorouracil phate mono- monophosphate CF₃ O2,4-O-Diacetyluracil phosphate mono- monophosphate CF₃ O Hypoxanthinephosphate mono- monophosphate CF₃ O 2,4-O-Diacetylthymine phosphatemono- monophosphate CF₃ O Thymine phosphate mono- monophosphate CF₃ OCytosine phosphate mono- monophosphate CF₃ O 4-(N-mono-acetyl)cytosinephosphate mono- monophosphate CF₃ O 4-(N,N-diacetyl)cytosine phosphatemono- monophosphate CF₃ O Uracil phosphate mono- monophosphate CF₃ O5-Fluorouracil phosphate mono- monophosphate CF₃ S 2,4-O-Diacetyluracilphosphate mono- monophosphate CF₃ S Hypoxanthine phosphate mono-monophosphate CF₃ S 2,4-O-Diacetylthymine phosphate mono- monophosphateCF₃ S Thymine phosphate mono- monophosphate CF₃ S Cyto sine phosphatemono- monophosphate CF₃ S 4-(N-mono-acetyl)cytosine phosphate mono-monophosphate CF₃ S 4-(N,N-diacetyl)cytosine phosphate mono-monophosphate CF₃ S Uracil phosphate mono- monophosphate CF₃ S5-Fluorouracil phosphate acetyl acetyl CF₃ O 4-(N,N-diacetyl)cytosineacetyl acetyl CF₃ S 4-(N,N-diacetyl)cytosine acetyl acetyl 2-bromo- O4-(N,N-diacetyl)cytosine vinyl acetyl acetyl 2-bromo- S4-(N,N-diacetyl)cytosine vinyl H H CH₃ O 2-(N,N-diacetyl)-guanine H HCH₃ O 6-O-acetyl guanine H H CH₃ O 8-fluoroguanine H H CH₃ O guanine H HCH₃ O 6-(N,N-diacetyl)-adenine H H CH₃ O 2-fluoroadenine H H CH₃ O8-fluoroadenine H H CH₃ O 2,6-difluoro-adenine H H CH₃ O adenine H H CH₃S 2-(N,N-diacetyl)-guanine H H CH₃ S 6-O-acetyl guanine H H CH₃ S8-fluoroguanine H H CH₃ S guanine H H CH₃ S 6-(N,N-diacetyl)-adenine H HCH₃ S 2-fluoroadenine H H CH₃ S 8-fluoroadenine H H CH₃ S2,6-difluoro-adenine H H CH₃ S adenine mono- H CH₃ O2-(N,N-diacetyl)-guanine phosphate mono- H CH₃ O 6-O-acetyl guaninephosphate mono- H CH₃ O 8-fluoroguanine phosphate mono- H CH₃ O guaninephosphate mono- H CH₃ O 6-(N,N-diacetyl)-adenine phosphate mono- H CH₃ O2-fluoroadenine phosphate mono- H CH₃ O 8-fluoroadenine phosphate mono-H CH₃ O 2,6-difluoro-adenine phosphate mono- H CH₃ O adenine phosphatemono- H CH₃ S 2-(N,N-diacetyl)-guanine phosphate mono- H CH₃ S6-O-acetyl guanine phosphate mono- H CH₃ S 8-fluoroguanine phosphatemono- H CH₃ S guanine phosphate mono- H CH₃ S 6-(N,N-diacetyl)-adeninephosphate mono- H CH₃ S 2-fluoroadenine phosphate mono- H CH₃ S8-fluoroadenine phosphate mono- H CH₃ S 2,6-difluoro-adenine phosphatemono- H CH₃ S adenine phosphate diphos- H CH₃ O 2-(N,N-diacetyl)-guaninephate diphos- H CH₃ O 6-O-acetyl guanine phate diphos- H CH₃ O8-fluoroguanine phate diphos- H CH₃ O guanine phate diphos- H CH₃ O6-(N,N-diacetyl)-adenine phate diphos- H CH₃ O 2-fluoroadenine phatediphos- H CH₃ O 8-fluoroadenine phate diphos- H CH₃ O2,6-difluoro-adenine phate diphos- H CH₃ O adenine phate diphos- H CH₃ S2-(N,N-diacetyl)-guanine phate diphos- H CH₃ S 6-O-acetyl guanine phatediphos- H CH₃ S 8-fluoroguanine phate diphos- H CH₃ S guanine phatediphos- H CH₃ S 6-(N,N-diacetyl)-adenine phate diphos- H CH₃ S2-fluoroadenine phate diphos- H CH₃ S 8-fluoroadenine phate diphos- HCH₃ S 2,6-difluoro-adenine phate diphos- H CH₃ S adenine phate triphos-H CH₃ O 2-(N,N-diacetyl)-guanine phate triphos- H CH₃ O 6-O-acetylguanine phate triphos- H CH₃ O 8-fluoroguanine phate triphos- H CH₃ Oguanine phate triphos- H CH₃ O 6-(N,N-diacetyl)-adenine phate triphos- HCH₃ O 2-fluoroadenine phate triphos- H CH₃ O 8-fluoroadenine phatetriphos- H CH₃ O 2,6-difluoro-adenine phate triphos- H CH₃ O adeninephate triphos- H CH₃ S 2-(N,N-diacetyl)-guanine phate triphos- H CH₃ S6-O-acetyl guanine phate triphos- H CH₃ S 8-fluoroguanine phate triphos-H CH₃ S guanine phate triphos- H CH₃ S 6-(N,N-diacetyl)-adenine phatetriphos- H CH₃ S 2-fluoroadenine phate triphos- H CH₃ S 8-fluoroadeninephate triphos- H CH₃ S 2,6-difluoro-adenine phate triphos- H CH₃ Sadenine phate mono- monophosphate CF₃ O 2-(N,N-diacetyl)-guaninephosphate mono- monophosphate CF₃ O 6-O-acetyl guanine phosphate mono-monophosphate CF₃ O 8-fluoroguanine phosphate mono- monophosphate CF₃ Oguanine phosphate mono- monophosphate CF₃ O 6-(N,N-diacetyl)-adeninephosphate mono- monophosphate CF₃ O 2-fluoroadenine phosphate mono-monophosphate CF₃ O 8-fluoroadenine phosphate mono- monophosphate CF₃ O2,6-difluoro-adenine phosphate mono- monophosphate CF₃ O adeninephosphate mono- monophosphate CF₃ S 2-(N,N-diacetyl)-guanine phosphatemono- monophosphate CF₃ S 6-O-acetyl guanine phosphate mono-monophosphate CF₃ S 8-fluoroguanine phosphate mono- monophosphate CF₃ Sguanine phosphate mono- monophosphate CF₃ S 6-(N,N-diacetyl)-adeninephosphate mono- monophosphate CF₃ S 2-fluoroadenine phosphate mono-monophosphate CF₃ S 8-fluoroadenine phosphate mono- monophosphate CF₃ S2,6-difluoro-adenine phosphate mono- monophosphate CF₃ S adeninephosphate acetyl acetyl CF₃ O guanine acetyl acetyl CF₃ S guanine acetylacetyl 2-bromo- O guanine vinyl acetyl acetyl 2-bromo- S guanine vinyl

[0305] Alternatively, the following nucleosides of Formula V areprepared, using the appropriate sugar and pyrimidine or purine bases.(V)

wherein: R¹ R⁶ X Base H CH₃ O 2,4-O-Diacetyluracil H CH₃ O HypoxanthineH CH₃ O 2,4-O-Diacetylthymine H CH₃ O Thymine H CH₃ O Cytosine H CH₃ O4-(N-mono-acetyl)cytosine H CH₃ O 4-(N,N-diacetyl)cytosine H CH₃ OUracil H CH₃ O 5-Fluorouracil H CH₃ S 2,4-O-Diacetyluracil H CH₃ SHypoxanthine H CH₃ S 2,4-O-Diacetylthymine H CH₃ S Thymine H CH₃ SCytosine H CH₃ S 4-(N-mono-acetyl)cytosine H CH₃ S4-(N,N-diacetyl)cytosine H CH₃ S Uracil monophosphate CH₃ S4-(N-mono-acetyl)cytosine monophosphate CH₃ S 4-(N,N-diacetyl)cytosinemonophosphate CH₃ S Uracil monophosphate CH₃ S 5-Fluorouracildiphosphate CH₃ O 2,4-O-Diacetyluracil diphosphate CH₃ O Hypoxanthinediphosphate CH₃ O 2,4-O-Diacetylthymine diphosphate CH₃ O Thyminediphosphate CH₃ O Cytosine diphosphate CH₃ O 4-(N-mono-acetyl)cytosinediphosphate CH₃ O 4-(N,N-diacetyl)cytosine diphosphate CH₃ O Uracildiphosphate CH₃ O 5-Fluorouracil diphosphate CH₃ S 2,4-O-Diacetyluracildiphosphate CH₃ S Hypoxanthine diphosphate CH₃ S 2,4-O-Diacetylthyminediphosphate CH₃ S Thymine diphosphate CH₃ S Cytosine triphosphate CH₃ O2,4-O-Diacetyluracil triphosphate CH₃ O Hypoxanthine triphosphate CH₃ O2,4-O-Diacetylthymine triphosphate CH₃ O Thymine triphosphate CH₃ OCytosine triphosphate CH₃ O 4-(N-mono-acetyl)cytosine triphosphate CH₃ O4-(N,N-diacetyl)cytosine triphosphate CH₃ O Uracil triphosphate CH₃ O5-Fluorouracil triphosphate CH₃ S 2,4-O-Diacetyluracil triphosphate CH₃S Hypoxanthine triphosphate CH₃ S 2,4-O-Diacetylthymine triphosphate CH₃S Thymine triphospahate CH₃ S Cytosine monophosphate CF₃ O2,4-O-Diacetyluracil monophosphate CF₃ O Hypoxanthine monophosphate CF₃O 2,4-O-Diacetylthymine monophosphate CF₃ O Thymine monophosphate CF₃ OCytosine monophosphate CF₃ O 4-(N-mono-acetyl)cytosine monophosphate CF₃O 4-(N,N-diacetyl)cytosine monophosphate CF₃ O Uracil monophosphate CF₃O 5-Fluorouracil monophosphate CF₃ S 2,4-O-Diacetyluracil monophosphateCF₃ S Hypoxanthine monophosphate CF₃ S 2,4-O-Diacetylthyminemonophosphate CF₃ S Thymine monophosphate CF₃ S Cytosine monophosphateCF₃ S 4-(N-mono-acetyl)cytosine monophosphate CF₃ S4-(N,N-diacetyl)cytosine monophosphate CF₃ S Uracil monophosphate CF₃ S5-Fluorouracil acetyl CF₃ O 4-(N,N-diacetyl)cytosine acetyl CF₃ S4-(N,N-diacetyl)cytosine acetyl 2-bromo-vinyl O 4-(N,N-diacetyl)cytosineacetyl 2-bromo-vinyl S 4-(N,N-diacetyl)cytosine

[0306] Alternatively, the following nucleosides of Formula VI areprepared, using the appropriate sugar and pyrimidine or purine bases.(VI)

wherein: R¹ R⁶ R⁷ R⁸ X Base R¹⁰ R⁹ H CH₃ H H O 2,4-O-Diacetyluracil OHMe H CH₃ H H O Hypoxanthine OH Me H CH₃ H H O 2,4-O-Diacetylthymine OHMe H CH₃ H H O Thymine OH Me H CH₃ H H O Cytosine OH Me H CH₃ H H O4-(N-mono-acetyl)cyto- OH Me sine H CH₃ H H O 4-(N,N-diacetyl)cytosineOH Me H CH₃ H H O Uracil OH Me H CH₃ H H O 5-Fluorouracil OH Me H CH₃ HH S 2,4-O-Diacetyluracil OH Me H CH₃ H H S Hypoxanthine OH Me H CH₃ H HS 2,4-O-Diacetylthymine OH Me H CH₃ H H S Thymine OH Me H CH₃ H H SCytosine OH Me H CH₃ H H S 4-(N-mono-acetyl)cyto- OH Me sine H CH₃ H H S4-(N,N-diacetyl)cytosine OH Me H CH₃ H H S Uracil OH Me H CH₃ H H S5-Fluorouracil OH Me mono- CH₃ H H O 2,4-O-Diacetyluracil OH Mephosphate mono- CH₃ H H O Hypoxanthine OH Me phosphate mono- CH₃ H H O2,4-O-Diacetylthymine OH Me phosphate mono- CH₃ H H O Thymine OH Mephosphate mono- CH₃ H H O Cytosine OH Me phosphate mono- CH₃ H H O4-(N-mono-acetyl)cyto- OH Me phosphate sine mono- CH₃ H H O4-(N,N-diacetyl)cytosine OH Me phosphate mono- CH₃ H H O Uracil OH Mephosphate mono- CH₃ H H O 5-Fluorouracil OH Me phosphate mono- CH₃ H H S2,4-O-Diacetyluracil OH Me phosphate mono- CH₃ H H S Hypoxanthine OH Mephosphate mono- CH₃ H H S 2,4-O-Diacetylthymine OH Me phosphate mono-CH₃ H H S Thymine OH Me phosphate mono- CH₃ H H S Cytosine OH Mephosphate mono- CH₃ H H S 4-(N-mono-acetyl)cyto- OH Me phosphate sinemono- CH₃ H H S 4-(N,N-diacetyl)cytosine OH Me phosphate mono- CH₃ H H SUracil OH Me phosphate mono- CH₃ H H S 5-Fluorouracil OH Me phosphatediphos- CH₃ H H O 2,4-O-Diacetyhiracil OH Me phate diphos- CH₃ H H OHypoxanthine OH Me phate diphos- CH₃ H H O 2,4-O-Diacetylthymine OH Mephate diphos- CH₃ H H O Thymine OH Me phate diphos- CH₃ H H O CytosineOH Me phate diphos- CH₃ H H O 4-(N-mono-acetyl)cyto- OH Me phate sinediphos- CH₃ H H O 4-(N,N-diacetyl)cytosine OH Me phate diphos- CH₃ H H OUracil OH Me phate diphos- CH₃ H H O 5-Fluorouracil OH Me phate diphos-CH₃ H H S 2,4-O-Diacetyluracil OH Me phate diphos- CH₃ H H SHypoxanthine OH Me phate diphos- CH₃ H H S 2,4-O-Diacetylthymine OH Mephate diphos- CH₃ H H S Thymine OH Me phate diphos- CH₃ H H S CytosineOH Me phate triphos- CH₃ H H O 2,4-O-Diacetyluracil OH Me phate triphos-CH₃ H H O Hypoxanthine OH Me phate triphos- CH₃ H H O2,4-O-Diacetylthymine OH Me phate triphos- CH₃ H H O Thymine OH Me phatetriphos- CH₃ H H O Cytosine OH Me phate triphos- CH₃ H H O4-(N-mono-acetyl)cyto- OH Me phate sine triphos- CH₃ H H O4-(N,N-diacetyl)cytosine OH Me phate triphos- CH₃ H H O Uracil OH Mephate triphos- CH₃ H H O 5-Fluorouracil OH Me phate triphos- CH₃ H H S2,4-O-Diacetyluracil OH Me phate triphos- CH₃ H H S Hypoxanthine OH Mephate triphos- CH₃ H H S 2,4-O-Diacetylthymine OH Me phate triphos- CH₃H H S Thymine OH Me phate triphos- CH₃ H H S Cytosine OH Me phate mono-CF₃ H H O 2,4-O-Diacetyluracil OH Me phosphate mono- CF₃ H H OHypoxanthine OH Me phosphate mono- CF₃ H H O 2,4-O-Diacetylthymine OH Mephosphate mono- CF₃ H H O Thymine OH Me phosphate mono- CF₃ H H OCytosine OH Me phosphate mono- CF₃ H H O 4-(N-mono-acetyl)cyto- OH Mephosphate sine mono- CF₃ H H O 4-(N,N-diacetyl)cytosine OH Me phosphatemono- CF₃ H H O Uracil OH Me phosphate mono- CF₃ H H O 5-Fluorouracil OHMe phosphate mono- CF₃ H H S 2,4-O-Diacetyluracil OH Me phosphate mono-CF₃ H H S Hypoxanthine OH Me phosphate mono- CF₃ H H S2,4-O-Diacetylthymine OH Me phosphate mono- CF₃ H H S Thymine OH Mephosphate mono- CF₃ H H S Cytosine OH Me phosphate mono- CF₃ H H S4-(N-mono-acetyl)cyto- OH Me phosphate sine mono- CF₃ H H S4-(N,N-diacetyl)cytosine OH Me phosphate mono- CF₃ H H S Uracil OH Mephosphate mono- CF₃ H H S 5-Fluorouracil OH Me phosphate acetyl CH₃ H HO 4-(N,N-diacetyl)cytosine H Br acetyl CH₃ H H S4-(N,N-diacetyl)cytosine H Br acetyl CH₃ OH H O 4-(N,N-diacetyl)cytosineH Br acetyl CH₃ OH H S 4-(N,N-diacetyl)cytosine H Br

[0307] VII. Anti-Hepatitis C Activity

[0308] Compounds can exhibit anti-hepatitis C activity by inhibiting HCVpolymerase, by inhibiting other enzymes needed in the replication cycle,or by other pathways. A number of assays have been published to assessthese activities. A general method that assesses the gross increase ofHCV virus in culture is disclosed in U.S. Pat. No. 5,738,985 to Miles etal. In vitro assays have been reported in Ferrari et al., Jnl. of Vir.,73:1649-1654, 1999; Ishii et al., Hepatology, 29:1227-1235,1999; Lohmannet al., Jnl. of Bio. Chem., 274:10807-10815, 1999; and Yamashita et al,Jnl. of Bio. Chem., 273:15479-15486, 1998.

[0309] WO 97/12033, filed on Sep. 27, 1996, by Emory University, listingC. Hagedorn and A. Reinoldus as inventors, and which claims priority toU.S. Ser. No. 60/004,383, filed on September 1995, describes an HCVpolymerase assay that can be used to evaluate the activity of thecompounds described herein. Another HCV polymerase assay has beenreported by Bartholomeusz, et al., Hepatitis C virus (HCV) RNApolymerase assay using cloned HCV non-structural proteins; AntiviralTherapy 1996:1(Supp 4) 18-24.

[0310] Screens that measure reductions in kinase activity from HCV drugsare disclosed in U.S. Pat. No. 6,030,785, to Katze et al., U.S. Pat. No.6,010,848 to Delvecchio et al, and U.S. Pat. No. 5,759,795 to Jubin etal. Screens that measure the protease inhibiting activity of proposedHCV drugs are disclosed in U.S. Pat. No. 5,861,267 to Su et al, U.S.Pat. No. 5,739,002 to De Francesco et al, and U.S. Pat. No. 5,597,691 toHoughton et al.

EXAMPLES

[0311] The test compounds were dissolved in DMSO at an initialconcentration of 200 μM and then were serially diluted in culturemedium.

[0312] Unless otherwise stated, baby hamster kidney (BHK-21) (ATCCCCL-10) and Bos Taurus (BT) (ATCC CRL 1390) cells were grown at 37° C.in a humidified CO₂ (5%) atmosphere. BHK-21 cells were passaged in EagleMEM additioned of 2 mM L-glutamine, 10% fetal bovine serum (FBS, Gibco)and Earle's BSS adjusted to contain 1.5 g/L sodium bicarbonate and 0.1mM non-essential amino acids. BT cells were passaged in Dulbecco'smodified Eagle's medium with 4 mM L-glutamine and 10% horse serum (HS,Gibco), adjusted to contain 1.5 g/L sodium bicarbonate, 4.5 g/L glucoseand 1.0 mM sodium pyruvate. The vaccine strain 17D (YFV-17D) (Stamaril®,Pasteur Merieux) and Bovine Viral Diarrhea virus (BVDV) (ATCC VR-534)were used to infect BHK and BT cells, respectively, in 75 cm² bottles.After a 3 day incubation period at 37° C., extensive cytopathic effectwas observed. Cultures were freeze-thawed three times, cell debris wereremoved by centrifugation and the supernatant was aliquoted and storedat −70° C. YFV-17D and BVDV were titrated in BHK-21 and BT cells,respectively, that were grown to confluency in 24-well plates.

Example 22

[0313] Phosphorylation Assay of Nucleoside to Active Triphosphate

[0314] To determine the cellular metabolism of the compounds, HepG2cells are obtained from the American Type Culture Collection (Rockville,Md.), and are grown in 225 cm² tissue culture flasks in minimalessential medium supplemented with non-essential amino acids, 1%penicillin-streptomycin. The medium is renewed every three days, and thecells are subcultured once a week. After detachment of the adherentmonolayer with a 10 minute exposure to 30 mL of trypsin-EDTA and threeconsecutive washes with medium, confluent HepG2 cells are seeded at adensity of 2.5×10⁶ cells per well in a 6-well plate and exposed to 10 μMof [³H] labeled active compound (500 dpm/pmol) for the specified timeperiods. The cells are maintained at 37° C. under a 5% CO₂ atmosphere.At the selected time points, the cells are washed three times withice-cold phosphate-buffered saline (PBS). Intracellular active compoundand its respective metabolites are extracted by incubating the cellpellet overnight at −20° C. with 60% methanol followed by extractionwith an additional 20 μL of cold methanol for one hour in an ice bath.The extracts are then combined, dried under gentle filtered air flow andstored at −20° C. until HPLC analysis.

Example 23

[0315] Bioavailability Assay in Cynomolgus Monkeys

[0316] Within 1 week prior to the study initiation, the cynomolgusmonkey is surgically implanted with a chronic venous catheter andsubcutaneous venous access port (VAP) to facilitate blood collection andunderwent a physical examination including hematology and serumchemistry evaluations and the body weight was recorded. Each monkey (sixtotal) receives approximately 250 μCi of ³H activity with each dose ofactive compound at a dose level of 10 mg/kg at a dose concentration of 5mg/mL, either via an intravenous bolus (3 monkeys, IV), or via oralgavage (3 monkeys, PO). Each dosing syringe is weighed before dosing togravimetrically determine the quantity of formulation administered.Urine samples are collected via pan catch at the designated intervals(approximately 18-0 hours pre-dose, 0-4, 4-8 and 8-12 hours post-dosage)and processed. Blood samples are collected as well (pre-dose, 0.25, 0.5,1, 2, 3, 6, 8, 12 and 24 hours post-dosage) via the chronic venouscatheter and VAP or from a peripheral vessel if the chronic venouscatheter procedure should not be possible. The blood and urine samplesare analyzed for the maximum concentration (C_(max)), time when themaximum concentration is achieved (T_(max)), area under the curve (AUC),half life of the dosage concentration (T_(½)), clearance (CL), steadystate volume and distribution (V_(ss)) and bioavailability (F).

Example 24

[0317] Bone Marrow Toxicity Assay

[0318] Human bone marrow cells are collected from normal healthyvolunteers and the mononuclear population are separated byFicoll-Hypaque gradient centrifugation as described previously bySommadossi J-P, Carlisle R. “Toxicity of 3′-azido-3′-deoxythymidine and9-(1,3-dihydroxy-2-propoxymethyl)guanine for normal human hematopoieticprogenitor cells in vitro” Antimicrobial Agents and Chemotherapy 1987;31:452-454; and Sommadossi J-P, Schinazi R F, Chu C K, Xie M-Y.“Comparison of cytotoxicity of the (−)- and (+)-enantiomer of2′,3′-dideoxy-3′-thiacytidine in normal human bone marrow progenitorcells” Biochemical Pharmacology 1992; 44:1921-1925. The culture assaysfor CFU-GM and BFU-E are performed using a bilayer soft agar ormethylcellulose method. Drugs are diluted in tissue culture medium andfiltered. After 14 to 18 days at 37° C. in a humidified atmosphere of 5%CO₂ in air, colonies of greater than 50 cells are counted using aninverted microscope. The results are presented as the percent inhibitionof colony formation in the presence of drug compared to solvent controlcultures.

Example 25

[0319] Mitochondria Toxicity Assay

[0320] HepG2 cells are cultured in 12-well plates as described above andexposed to various concentrations of drugs as taught by Pan-Zhou X-R,Cui L, Zhou X-J, Sommadossi J-P, Darley-Usmer V M. “Differential effectsof antiretroviral nucleoside analogs on mitochondrial function in HepG2cells” Antimicrob Agents Chemother 2000; 44:496-503. Lactic acid levelsin the culture medium after 4 day drug exposure are measured using aBoehringer lactic acid assay kit. Lactic acid levels are normalized bycell number as measured by hemocytometer count.

Example 26

[0321] Cytotoxicity Assay

[0322] Cells are seeded at a rate of between 5×10³ and 5×10⁴/well into96-well plates in growth medium overnight at 37° C. in a humidified CO₂(5%) atmosphere. New growth medium containing serial dilutions of thedrugs is then added. After incubation for 4 days, cultures are fixed in50% TCA and stained with sulforhodamineB. The optical density was readat 550 nm. The cytotoxic concentration was expressed as theconcentration required to reduce the cell number by 50% (CC₅₀). Thepreliminary results are tabulated in the Table 1 below. TABLE 1 MDBKversus Human Hepatoma CC₅₀, μM Compound MDBK β-D-4′-CH₃-riboG >250β-D-4′-CH₃-ribo-4- >250 thioU β-D-4′-CH₃-riboC >250β-D-4′-CH₃-ribo-5- >167 fluoroU β-D-4′-CH₃-riboT >250 β-D-4′-CH₃-riboA>250

[0323] This invention has been described with reference to its preferredembodiments. Variations and modifications of the invention, will beobvious to those skilled in the art from the foregoing detaileddescription of the invention.

We claim:
 1. A compound of Formula I:

or a pharmaceutically acceptable salt or prodrug thereof, wherein: R¹,R² and R³ are independently H, mono-phosphate, di-phosphate,tri-phosphate; a stabilized phosphate prodrug; acyl; alkyl; sulfonateester; a lipid, a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² and R³ are independently H or phosphate; Y is hydrogen,bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ and X² areindependently selected from the group consisting of H, alkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ orSR⁴; and R⁴ and R⁵ are independently hydrogen, acyl, or alkyl.
 2. Acompound of Formula II:

or a pharmaceutically acceptable salt or prodrug thereof, wherein: R¹,R² and R³ are independently H, mono-phosphate, di-phosphate,tri-phosphate, a stabilized phosphate prodrug; acyl; alkyl; sulfonateester; a lipid, a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² and R³ are independently H or phosphate; Y is hydrogen,bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ is selected from thegroup consisting of H, alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴ and R⁵ are independentlyhydrogen, acyl, or alkyl.
 3. A compound selected from Formulas III, IVand V, or a pharmaceutically acceptable salt or prodrug thereof, isprovided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 4. A compound of Formula III, IV or V, or a pharmaceuticallyacceptable salt or prodrug thereof, is provided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently hydrogen or phosphate; R⁶ is alkyl; and X is O, S, SO₂ orCH₂.
 5. A compound of Formula III, IV or V, or a pharmaceuticallyacceptable salt or prodrug thereof, is provided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ arehydrogens; R⁶ is alkyl; and X is O, S, SO₂ or CH₂.
 6. A compound ofFormula III, IV or V, or a pharmaceutically acceptable salt or prodrugthereof, is provided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently hydrogen or phosphate; R⁶ is alkyl; and X is O.
 7. Acompound of Formula IV, or its pharmaceutically acceptable salt orprodrug, is provided:

wherein: Base is a purine or pyrimidine base; optionally substitutedwith an amine or cyclopropyl; and R¹ and R² are independently H;mono-phosphate, di-phosphate, tri-phosphate, a stabilized phosphateprodrug; acyl; alkyl; sulfonate ester; a lipid, a phospholipid; an aminoacid; a carbohydrate; a peptide; a cholesterol; or otherpharmaceutically acceptable leaving group which when administered invivo is capable of providing a compound wherein R¹ or R² isindependently H or phosphate.
 8. A compound of Formula VI, or apharmaceutically acceptable salt or prodrug thereof:

wherein: Base is a purine or pyrimidine base; R¹ and R² areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ or R²is independently H or phosphate; R⁶ is hydroxy, alkyl, azido, cyano,alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, —N(acyl)₂; R⁷ and R⁹ are independently hydrogen, OR²,hydroxy, alkyl, azido, cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂, —NH(loweralkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; R⁸ and R¹⁰ areindependently H, alkyl, chlorine, bromine or iodine; alternatively, R⁷and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can come together to form api bond; and X is O, S, SO₂ or CH₂.
 9. A compound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 10. A compoundof the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 11. A compoundof the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 12. A compoundof the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 13. A compoundof the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 14. A compoundof the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 15. Thecompound as described in any of the preceding claims 1-14, wherein thesaid compound is in the form of a dosage unit.
 16. The compound asdescribed in claim 15, wherein the dosage unit contains 10 to 1500 mg ofsaid compound.
 17. The compound as described in claim 15 or 16, whereinsaid dosage unit is a tablet or capsule.
 18. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of Formula I:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent, wherein: R¹, R² and R³are independently hydrogen, mono-phosphate, di-phosphate, tri-phosphate;a stabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²and R³ are independently hydrogen or phosphate; Y is hydrogen, bromo,chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ and X² are independentlyselected from the group consisting of hydrogen, alkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ orSR⁴; and R⁴ and R⁵ are independently hydrogen, acyl, or alkyl.
 19. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of Formula II:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent, wherein: R¹, R² and R³are independently H, mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²and R³ are independently H or phosphate; Y is hydrogen, bromo, chloro,fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ is selected from the groupconsisting of H, alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴ and R⁵ are independentlyhydrogen, acyl, or alkyl.
 20. A pharmaceutical composition for thetreatment or prophylaxis of a hepatitis C virus in a host, comprising aneffective amount of a compound selected from Formulas III, IV and V, ora pharmaceutically acceptable salt or prodrug thereof, is provided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester, a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 21. A pharmaceutical composition for the treatment orprophylaxis of a hepatitis C virus in a host, comprising an effectiveamount of a compound of Formula VI, or a pharmaceutically acceptablesalt or prodrug thereof:

wherein: Base is a purine or pyrimidine base; R¹ and R² areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester, a lipid,including a phospholipid; an amino acid; a carbohydrate; a peptide; acholesterol; or other pharmaceutically acceptable leaving group whichwhen administered in vivo is capable of providing a compound wherein R¹or R² is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, —N(acyl)₂; R⁷ and R⁹ are independently hydrogen, OR²,hydroxy, alkyl, azido, cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂, —NH(loweralkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; R⁸ and R¹⁰ areindependently H, alkyl , chlorine, bromine or iodine; alternatively, R⁷and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can come together to form api bond; and X is O, S, SO₂ or CH₂.
 22. A pharmaceutical composition forthe treatment or prophylaxis of a hepatitis C virus in a host,comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 23. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 24. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 25. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 26. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 27. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, together witha pharmaceutically acceptable carrier or diluent.
 28. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of Formula I:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents, wherein: R¹, R² andR³ are independently H, mono-phosphate, di-phosphate, tri-phosphate; astabilized phosphate prodrug; acyl; alkyl; sulfonate ester, a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²and R³ are independently H or phosphate; Y is hydrogen, bromo, chloro,fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ and X² are independently selectedfrom the group consisting of H, alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴ NR⁴NR⁵ or SR⁴; and R⁴and R⁵ are independently hydrogen, acyl, or alkyl.
 29. A pharmaceuticalcomposition for the treatment or prophylaxis of a hepatitis C virus in ahost, comprising an effective amount of a compound of Formula IV:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents, wherein: R¹, R² andR³ are independently H, mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester, a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²and R³ are independently H or phosphate; Y is hydrogen, bromo, chloro,fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ is selected from the groupconsisting of H, alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴ and R⁵ are independentlyhydrogen, acyl, or alkyl.
 30. A pharmaceutical composition for thetreatment or prophylaxis of a hepatitis C virus in a host, comprising aneffective amount of a compound selected from Formulas III, IV and V, ora pharmaceutically acceptable salt or prodrug thereof, is provided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; phosphate mono-phosphate, di-phosphate, tr-iphosphate,a stabilized phosphate prodrug; acyl; alkyl; sulfonate ester, a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 31. A pharmaceutical composition for the treatment orprophylaxis of a hepatitis C virus in a host, comprising an effectiveamount of a compound of Formula VI, or a pharmaceutically acceptablesalt or prodrug thereof:

wherein: Base is a purine or pyrimidine base; R¹ and R² areindependently H; phosphate mono-phosphate, di-phosphate, tri-phosphate,a stabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹ or R²is independently H or phosphate; R⁶ is hydroxy, alkyl, azido, cyano,alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl),—O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl),chloro, bromo, fluoro, iodo, NO₂, NH₂, —NH(lower alkyl), —NH(acyl),—N(lower alkyl)₂, —N(acyl)₂; R⁷ and R⁹ are independently hydrogen, OR²,hydroxy, alkyl, azido, cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂, —NH(loweralkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; R⁸ and R¹⁰ areindependently H, alkyl, chlorine, bromine or iodine; alternatively, R⁷and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can come together to form api bond; and X is O, S, SO₂ or CH₂.
 32. A pharmaceutical composition forthe treatment or prophylaxis of a hepatitis C virus in a host,comprising an effective amount of a compound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 33. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 34. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 35. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 36. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 37. Apharmaceutical composition for the treatment or prophylaxis of ahepatitis C virus in a host, comprising an effective amount of acompound of structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationwith one or more other antivirally effective agents.
 38. Thepharmaceutical composition as described in any of the preceding claims18-37, wherein the said compound is in the form of a dosage unit. 39.The pharmaceutical composition as described in claim 38, wherein thedosage unit contains 10 to 1500 mg of said compound.
 40. Thepharmaceutical composition as described in claim 38 or 39, wherein saiddosage unit is a tablet or capsule.
 41. A method for the treatment orprophylaxis of a hepatitis C virus infection in a host, comprisingadministering an anti-virally effective amount of a compound of FormulaI:

or a pharmaceutically acceptable salt or prodrug thereof, wherein: R¹,R² and R³ are independently H, mono-phosphate, di-phosphate,tri-phosphate; a stabilized phosphate prodrug; acyl; alkyl; sulfonateester; a lipid, a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² and R³ are independently H or phosphate; Y is hydrogen,bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ and X² areindependently selected from the group consisting of H, alkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ orSR⁴; and R⁴ and R⁵ are independently hydrogen, acyl, or alkyl.
 42. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an anti-virally effective amount ofa compound of Formula II:

or a pharmaceutically acceptable salt or prodrug thereof, wherein: R¹,R² and R³ are independently H, mono-phosphate, di-phosphate,tri-phosphate, a stabilized phosphate prodrug; acyl; alkyl; sulfonateester; a lipid, a phospholipid; an amino acid; a carbohydrate; apeptide; a cholesterol; or other pharmaceutically acceptable leavinggroup which when administered in vivo is capable of providing a compoundwherein R¹, R² and R³ are independently H or phosphate; Y is hydrogen,bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁴; X¹ is selected from thegroup consisting of H, alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴ and R⁵ are independentlyhydrogen, acyl, or alkyl.
 43. A method for the treatment or prophylaxisof a hepatitis C virus infection in a host, comprising administering ananti-virally effective amount of a compound selected from Formulas III,IV and V, or a pharmaceutically acceptable salt or prodrug thereof, isprovided:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 44. A method for the treatment or prophylaxis of a hepatitisC virus infection in a host, comprising administering an anti-virallyeffective amount of a compound of Formula VI, or a pharmaceuticallyacceptable salt or prodrug thereof:

wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 45. A method for the treatment or prophylaxis of a hepatitisC virus infection in a host, comprising administering an antivirallyeffective amount of a compound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 46. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 47. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 48. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 49. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 50. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof.
 51. A methodfor the treatment or prophylaxis of a hepatitis C virus infection in ahost, comprising administering an anti-virally effective amount of acompound of Formula I:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more other antivirally effective agents,wherein: R¹, R² and R³ are independently H, mono-phosphate,di-phosphate, tri-phosphate; a stabilized phosphate prodrug; acyl;alkyl; sulfonate ester; a lipid, a phospholipid; an amino acid; acarbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² and R³ are independently H orphosphate; Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ orSR⁴; X¹ and X² are independently selected from the group consisting ofH, alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro,iodo, OR⁴, NR⁴NR⁵ or SR⁴; and R⁴ and R⁵ are independently hydrogen,acyl, or alkyl.
 52. A method for the treatment or prophylaxis of ahepatitis C virus infection in a host, comprising administering ananti-virally effective amount of a compound of Formula II:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more other antivirally effective agents,wherein: R¹, R² and R³ are independently H, mono-phosphate,di-phosphate, tri-phosphate, a stabilized phosphate prodrug; acyl;alkyl; sulfonate ester; a lipid, a phospholipid; an amino acid; acarbohydrate; a peptide; a cholesterol; or other pharmaceuticallyacceptable leaving group which when administered in vivo is capable ofproviding a compound wherein R¹, R² and R³ are independently H orphosphate; Y is hydrogen, bromo, chloro, fluoro, iodo, OR⁴, NR⁴R⁵ orSR⁴; X¹ is selected from the group consisting of H, alkyl, CO-alkyl,CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴NR⁵ orSR⁴; and R⁴ and R⁵ are independently hydrogen, acyl, or alkyl.
 53. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an anti-virally effective amount ofa compound selected from Formulas III, IV and V:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more other antivirally effective agents,wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; and X is O, S,SO₂ or CH₂.
 54. A method for the treatment or prophylaxis of a hepatitisC virus infection in a host, comprising administering an anti-virallyeffective amount of a compound of Formula VI, or a pharmaceuticallyacceptable salt or prodrug thereof:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more other antivirally effective agents,wherein: Base is a purine or pyrimidine base; R¹, R² and R³ areindependently H; mono-phosphate, di-phosphate, tri-phosphate, astabilized phosphate prodrug; acyl; alkyl; sulfonate ester; a lipid, aphospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol;or other pharmaceutically acceptable leaving group which whenadministered in vivo is capable of providing a compound wherein R¹, R²or R³ is independently H or phosphate; R⁶ is hydroxy, alkyl, azido,cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, —C(O)O(alkyl),—C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(loweralkyl), —O(alkenyl), CF₃, chloro, bromo, fluoro, iodo, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; X is O, S, SO₂or CH₂. R⁷ and R⁹ are independently hydrogen, OR², hydroxy, alkyl(including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl,—C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl),—O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO₂, NH₂,—NH(lower alkyl), —NH(acyl), —N(lower alkyl)₂, —N(acyl)₂; R⁸ and R¹⁰ areindependently H, alkyl, chlorine, bromine or iodine; alternatively, R⁷and R⁹, R⁷ and R¹⁰, R⁸ and R⁹, or R⁸ and R¹⁰ can come together to form api bond; and X is O, S, SO₂ or CH₂.
 55. A method for the treatment orprophylaxis of a hepatitis C virus infection in a host, comprisingadministering an antivirally effective amount of a compound of thestructure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 56. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 57. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 58. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 59. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 60. Amethod for the treatment or prophylaxis of a hepatitis C virus infectionin a host, comprising administering an antivirally effective amount of acompound of the structure:

or a pharmaceutically acceptable salt or prodrug thereof, in combinationor alternation with one or more antivirally effective agents.
 61. Methodof treatment as described in any of the preceding claims 51-60, whereinthe said compound is in the form of a dosage unit.
 62. Method oftreatment as described in claim 61, wherein the dosage unit contains 10to 1500 mg of said compound.
 63. Method of treatment as described inclaim 61 or 62, wherein said dosage unit is a tablet or capsule.
 64. Acompound as in claims 3, 4, 5, 6, 7, or 8, in which the purine orpyrimidine base is selected from the group comprising of

wherein A, G, and L are each independently CH or N; D is N, CH, C—CN,C—NO₂, C—C₁₋₃ alkyl, C—NHCONH₂, C—CONQ¹¹Q¹¹, C—CSNQ¹¹Q¹¹, CCOOQ¹¹,C—C(═NH)NH₂, C-hydroxy, C—C₁₋₃alkoxy, C-amino, C—C₁₋₄ alkylamino,C-di(C₁₋₄ alkyl)amino, C-halogen, C-(1,3-oxazol-2-yl),C-(1,3-thiazol-2-yl), or C-(imidazol-2-yl); wherein alkyl isunsubstituted or substituted with one to three groups independentlyselected from halogen, amino, hydroxy, carboxy, and C₁₋₃ alkoxy; E is Nor CQ⁵; W is O, S, or NR; R is H, OH, alkyl; Q⁶ is H, OH, SH, NH₂, C₁₋₄alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, halogen, C₁₋₄alkyl, C₁₋₄ alkoxy, or CF₃; Q⁵ is H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆alkynyl, C₁₋₄ alkylamino, CF₃, halogen, N, CN, NO₂, NHCONH₂, CONQ¹¹Q¹¹,CSNQ¹¹Q¹¹, COOQ¹¹, C(═NH)NH₂, hydroxy, C₁₋₃alkoxy, amino, C₁₋₄alkylamino, di(C₁₋₄ alkyl)amino, halogen, 1,3-oxazol-2-yl,1,3-thiazol-2-yl, or imidazol-2-yl; wherein alkyl is unsubstituted orsubstituted with one to three groups independently selected fromhalogen, amino, hydroxy, carboxy, and C₁₋₃ alkoxy; Q⁷ and Q¹⁴ are eachindependently selected from the group consisting of H, CF₃, OH, SH, OR,SR C₁₋₄ alkyl, amino, C₁₋₄ alkylamino, C₃₋₆ cycloalkylamino, and di(C₁₋₄alkyl)amino; Q¹¹ is independently H or C₁₋₆ alkyl; Q⁸ is H, halogen, CN,carboxy, C₁₋₄ alkyloxycarbonyl, N₃, amino, C₁₋₄ alkylamino, di(C₁₋₄alkyl)amino, hydroxy, C₁₋₆ alkoxy, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl,(C₁₋₄ alkyl)0-2 aminomethyl, N, CN, NO₂, C₁₋₃ alkyl, NHCONH₂, CONQ¹¹Q¹¹,CSNQ¹¹Q¹¹, COOQ¹¹, C(═NH)NH₂, 1,3-oxazol-2-yl, 1,3-thiazol-2-yl, orimidazol-2-yl, wherein alkyl is unsubstituted or substituted with one tothree groups independently selected from halogen, amino, hydroxy,carboxy, and C₁₋₃ alkoxy.
 65. A compound as in claims 3, 4, 5, 6, 7, or8, in which the purine or pyrimidine base is selected from the followinggroup:

wherein: T₁ and T₂ are independently selected from N, CH, or C—Q¹⁶; Q¹⁶,U, and Y are independently selected from O, H, OH, substituted orunsubstituted alkyl, substituted or unsubstituted alkenyl, substitutedor unsubstituted alkynyl, cycloalkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵, Br-vinyl, —O-alkyl,—O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl, —O-acyl, —O-cycloalkyl,NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl, N-aralkyl, NH-cycloalkyl, SH,S-alkyl, S-acyl, S-aryl, S-cycloalkyl, S-aralkyl, CN, N₃, COOH, CONH₂,CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH, CF₃, CH₂OH, (CH₂)_(m)OH,(CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN, (CH₂)_(m)NO₂, (CH₂)_(m)CONH₂,C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, C₁₋₄ alkoxy,C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂aminomethyl, or —NHC(═NH)NH₂; R⁴ and R⁵ are independently selected fromhydrogen, acyl, or alkyl; m is 0-10; Z is S, SO, SO2, C═O, or NQ²⁰; Q²⁰is H or alkyl; and V₁ and V₂ are independently selected from CH or N;66. A compound as in claims 3, 4, 5, 6, 7, or 8, in which the purine orpyrimidine base is selected from the following group:

wherein: T₃ and T₄ are independently selected from N or CQ²²; Q²² isindependently selected from O, H, OH, substituted or unsubstitutedalkyl, substituted or unsubstituted alkenyl, substituted orunsubstituted alkynyl, cycloalkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵, Br-vinyl, —O-alkyl,—O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl, —O-acyl, —O-cycloalkyl,NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl, N-aralkyl, NH-cycloalkyl, SH,S-alkyl, S-acyl, S-aryl, S-cycloalkyl, S-aralkyl, CN, N₃, COOH, CONH₂,CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH, CF₃, CH₂OH, (CH₂)_(m)OH,(CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN, (CH₂)_(m)NO₂, (CH₂)_(m)CONH₂,C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, C₁₋₄ alkoxy,C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂aminomethyl, or —NHC(═NH)NH₂; R⁴ and R⁵ are independently selected fromhydrogen, acyl, or alkyl; m is 0-10; T₆, T₇, T₈, T₉, T₁₀, T₁₁, and T₁₂are independently selected from N or CH; U₂ is H, straight chained,branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵; Y₂ is O, S, NH, NR or CQ²⁴Q²⁶where R is H, OH, or alkyl; Q²⁴ and Q²⁶ are independently selected fromH, alkyl, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵.
 67. Amethod of treatment or prophylaxis as in claims 43, 44, 53, or 54, inwhich the purine or pyrimidine base is selected from the groupcomprising of.

wherein A, G, and L are each independently CH or N; D is N, CH, C—CN,C—NO₂, C—C₁₋₃ alkyl, C—NHCONH₂, C—CONQ¹¹Q¹¹, C—CSNQ¹¹Q¹¹, CCOOQ¹¹,C—C(═NH)NH₂, C-hydroxy, C—C₁₋₃alkoxy, C-amino, C—C₁₋₄ alkylamino,C-di(C₁₋₄ alkyl)amino, C-halogen, C-(1,3-oxazol-2-yl),C-(1,3-thiazol-2-yl), or C-(imidazol-2-yl); wherein alkyl isunsubstituted or substituted with one to three groups independentlyselected from halogen, amino, hydroxy, carboxy, and C₁₋₃ alkoxy; E is Nor CQ⁵; W is O, S, or NR; R is H, OH, alkyl; Q⁶ is H, OH, SH, NH₂, C₁₋₄alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, halogen, C₁₋₄alkyl, C₁₋₄ alkoxy, or CF₃; Q⁵ is H, C₁₋₆ alkyl, C₂₋₆ alkenyl, C₂₋₆alkynyl, C₁₋₄ alkylamino, CF₃, halogen, N, CN, NO₂, NHCONH₂, CONQ¹¹Q¹¹,CSNQ¹¹Q¹¹, COOQ¹¹, C(═NH)NH₂, hydroxy, C₁₋₃alkoxy, amino, C₁₋₄alkylamino, di(C₁₋₄ alkyl)amino, halogen, 1,3-oxazol-2-yl,1,3-thiazol-2-yl, or imidazol-2-yl; wherein alkyl is unsubstituted orsubstituted with one to three groups independently selected fromhalogen, amino, hydroxy, carboxy, and C₁₋₃ alkoxy; Q⁷ and Q¹⁴ are eachindependently selected from the group consisting of H, CF₃, OH, SH, OR,SR C₁₋₄ alkyl, amino, C₁₋₄ alkylamino, C₃₋₆ cycloalkylamino, and di(C₁₋₄alkyl)amino; Q¹¹ is independently H or C₁₋₆ alkyl; Q⁸ is H, halogen, CN,carboxy, C₁₋₄ alkyloxycarbonyl, N₃, amino, C₁₋₄ alkylamino, di(C₁₋₄alkyl)amino, hydroxy, C₁₋₆ alkoxy, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl,(C₁₋₄ alkyl)0-2 aminomethyl, N, CN, NO₂, C₁₋₃ alkyl, NHCONH₂, CONQ¹¹Q¹¹,CSNQ¹¹Q¹¹, COOQ¹¹, C(═NH)NH₂, 1,3-oxazol-2-yl, 1,3-thiazol-2-yl, orimidazol-2-yl, wherein alkyl is unsubstituted or substituted with one tothree groups independently selected from halogen, amino, hydroxy,carboxy, and C₁₋₃ alkoxy.
 68. A method of treatment or prophylaxis as inclaims 43, 44, 53, or 54, in which the purine or pyrimidine base isselected from the group comprising of:

wherein: T₁ and T₂ are independently selected from N, CH, or C—Q¹⁶; Q¹⁶,U, and Y are independently selected from O, H, OH, substituted orunsubstituted alkyl, substituted or unsubstituted alkenyl, substitutedor unsubstituted alkynyl, cycloalkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵, Br-vinyl, —O-alkyl,—O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl, —O-acyl, —O-cycloalkyl,NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl, N-aralkyl, NH-cycloalkyl, SH,S-alkyl, S-acyl, S-aryl, S-cycloalkyl, S-aralkyl, CN, N₃, COOH, CONH₂,CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH, CF₃, CH₂OH, (CH₂)_(m)OH,(CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN, (CH₂)_(m)NO₂, (CH₂)_(m)CONH₂,C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, C₁₋₄ alkoxy,C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂aminomethyl, or —NHC(═NH)NH₂; R⁴ and R⁵ are independently selected fromhydrogen, acyl, or alkyl; m is 0-10; Z is S, SO, SO₂, C═O, or NQ²⁰; Q₂₀is H or alkyl; and V¹ and V₂ are independently selected from CH or N;69. A method of treatment or prophylaxis as in claims 43, 44, 53, or 54,in which the purine or pyrimidine base is selected from the groupcomprising of:

wherein: T₃ and T₄ are independently selected from N or CQ²²; Q²² isindependently selected from O, H, OH, substituted or unsubstitutedalkyl, substituted or unsubstituted alkenyl, substituted orunsubstituted alkynyl, cycloalkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl,chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵, Br-vinyl, —O-alkyl,—O-alkenyl, —O-alkynyl, —O-aryl, —O-aralkyl, —O-acyl, —O-cycloalkyl,NH₂, NH-alkyl, N-dialkyl, NH-acyl, N-aryl, N-aralkyl, NH-cycloalkyl, SH,S-alkyl, S-acyl, S-aryl, S-cycloalkyl, S-aralkyl, CN, N₃, COOH, CONH₂,CO₂-alkyl, CONH-alkyl, CON-dialkyl, OH, CF₃, CH₂OH, (CH₂)_(m)OH,(CH₂)_(m)NH₂, (CH₂)_(m)COOH, (CH₂)_(m)CN, (CH₂)_(m)NO₂, (CH₂)_(m)CONH₂,C₁₋₄ alkylamino, di(C₁₋₄ alkyl)amino, C₃₋₆ cycloalkylamino, C₁₋₄ alkoxy,C₁₋₄ alkoxycarbonyl, C₁₋₆ alkylthio, C₁₋₆ alkylsulfonyl, (C₁₋₄ alkyl)₀₋₂aminomethyl, or —NHC(═NH)NH₂; R⁴ and R⁵ are independently selected fromhydrogen, acyl, or alkyl; m is 0-10; T₆, T₇, T₈, T₉, T₁₀, T₁₁, and T₁₂are independently selected from N or CH; U₂ is H, straight chained,branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro,bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵; Y₂ is O, S, NH, NR or CQ²⁴Q²⁶where R is H, OH, or alkyl; Q²⁴ and Q²⁶ are independently selected fromH, alkyl, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl,CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR⁴, NR⁴R⁵ or SR⁵.